Neuromodulation stimulation for the restoration of sexual function

ABSTRACT

Systems and methods use an implantable pulse generator system for neuromodulation stimulation to treat sexual dysfunction by the unilateral or bilateral stimulation of the left and/or right branches of the dorsal genital nerves using one or more leads and electrodes implanted in adipose or other tissue in the region at or near the pubic symphysis. A neuromodulation stimulation waveform includes at least a variable frequency component and/or a variable duty cycle component and/or a variable amplitude component and/or a variable pause component to ward off habituation.

RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 11/149,654, filed 10 Jun. 2005, and entitled“Systems and Methods for Bilateral Stimulation of Left and RightBranches of the Dorsal Genital Nerves to Treat Dysfunctions Such asUrinary Incontinence.” This application also claims the benefit of U.S.Provisional Patent Application Ser. No. 60/578,742, filed Jun. 10, 2004,and entitled “Systems and Methods for Bilateral Stimulation of Left andRight Branches of the Dorsal Genital Nerves to Treat Dysfunctions, Suchas Urinary Incontinence,” which are all incorporated herein byreference.

This application is also a continuation-in-part of co-pending U.S.patent application Ser. No. 11/150,419, filed 10 Jun. 2005, and entitled“Lead and Electrode Structures Sized and Configured for Implantation inAdipose Tissue and Associated Methods of Implantation,” which isincorporated herein by reference.

This application is also a continuation-in-part of co-pending U.S.patent application Ser. No. 11/150,535, filed 10 Jun. 2005, and entitled“Implantable Pulse Generator for Providing Functional and/or TherapeuticStimulation of Muscles and/or Nerves and/or Central Nervous SystemTissue.” This application also claims the benefit of U.S. ProvisionalPatent Application Ser. No. 60/578,742, filed Jun. 10, 2004, andentitled “Systems and Methods for Bilateral Stimulation of Left andRight Branches of the Dorsal Genital Nerves to Treat Dysfunctions, Suchas Urinary Incontinence,” and U.S. Provisional Patent Application Ser.No. 60/599,193, filed Aug. 5, 2004, and entitled “Implantable PulseGenerator for Providing Functional and/or Therapeutic Stimulation ofMuscles and/or Nerves,” and U.S. Provisional Patent Application Ser. No.60/680,598, filed May 13, 2005, and entitled “Implantable PulseGenerator for Providing Functional and/or Therapeutic Stimulation ofMuscles and/or Nerves and/or Central Nervous System Tissue,” which areall incorporated herein by reference.

This application is also a continuation-in-part of co-pending U.S.patent application Ser. No. 11/196,995, filed 4 Aug. 2005, and entitled“Devices, Systems, and Methods Employing a Molded Nerve Cuff Electrode.”This application also claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/598,695, filed Aug. 4, 2004, and entitled“Devices, Systems, and Methods Employing a Molded Nerve Cuff Electrode,”which are all incorporated herein by reference.

This application is also a continuation-in-part of co-pending U.S.patent application Ser. No. 10/662,055, filed 12 Sep. 2003, and entitled“Systems and Methods for Stimulating Components In, On, or Near thePudendal Nerve or its Branches to Achieve Selective PhysiologicResponses,” which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to systems and methods for neuromodulationstimulation for the restoration of sexual function in animals, includinghumans.

BACKGROUND OF THE INVENTION

I. Neuromodulation Stimulation

Neuromodulation stimulation (the electrical excitation of nerves, oftenafferent nerves, to indirectly affect the stability or performance of aphysiological system) can provide functional and/or therapeuticoutcomes. While existing systems and methods can provide remarkablebenefits to individuals requiring neuromodulation stimulation, manylimitations and issues still remain. For example, existing systems canoften require the user to wear an external stimulator, which may providea positive functional outcome, but may also negatively affect quality oflife issues.

A variety of products and treatment methods are available forneuromodulation stimulation. As an example, neuromodulation stimulationhas been used for the treatment of sexual dysfunction, which affectsboth men and women. A wide range of options exist for the restoration ofsexual function. Treatments include everything from medications, simplemechanical devices, psychological counseling, external stimulators, andsurgically implanted devices.

Both external and implantable devices are available for the purpose ofneuromodulation stimulation for the restoration of sexual function. Theoperation of these devices typically includes the use of an electrodeplaced either on the external surface of the skin or a surgicallyimplanted electrode. Although these modalities have shown the ability toprovide a neuromodulation stimulation with positive effects, they havereceived limited acceptance by patients because of their limitations ofportability, limitations of treatment regimes, and limitations of easeof use and user control.

II. Sexual Dysfunction

One form of male sexual dysfunction is know as Erectile Dysfunction(ED), and is often referred to as “impotency.” There are some commondiseases such as diabetes, Peyronie's disease, heart disease, andprostate cancer that are associated with impotency or have treatmentsthat may cause impotency. And in some cases the cause may bepsychological.

Erectile Dysfunction is common problem affecting men and is defined asthe inability to achieve or maintain a penile erection sufficient forsexual activity. It is estimated that 35% to 50% of all men aged 40 to70 have some form of ED, nearly 46 million Americans have ED, and over150 million men have ED worldwide. It is also estimated that sexualdysfunctions occur in 43 percent of women in the United States. It wouldcost $3.5 billion per year if only one fifth of Americans with ED weretreated with the first line of treatment (oral therapy such as PDE-5inhibitors), and the cost for the second line of treatment (such asinjection or transurethral administration of alprostadil) isapproximately twice as expensive. A cost-effective therapy is neededbecause the number of men seeking treatment tripled between 1997 and2000 and is expected to increase as awareness of treatment options forED becomes more widespread.

The severity of erectile dysfunction can range from 1) mild ED, in whicha man is occasionally unable to achieve and sustain an erectionsufficient for intercourse, to 2) frequent or moderate ED to 3) severeor complete ED, in which a man is never able to produce and sustain anerection sufficient for intercourse. The prevalence of moderate tocomplete ED increases with age. Approximately 20% of men aged 40 yearshave moderate to severe ED and approximately 70% of men aged 70 yearshave moderate to severe ED. Over 70% of men with ED report that theirquality of life is moderately to severely reduced by ED, and over 70% ofmen with ED feel hurt by the response of their partner to their ED andfeel “to some extent a failure” because of their ED. Thus, ED is oftenassociated with poor self-image, depression, and it can affectinterpersonal relationships and lead to increased mental stress.

ED is often a result of a combination of psychological and organicfactors, but it is thought to be purely psychological in origin in lessthan 30% of the cases. Organic factors can include complications fromneurologic diseases (stroke, multiple sclerosis, Alzheimer's disease,brain or spinal tumors), chronic renal failure, prostate cancer,diabetes, trauma, surgery, medications, and abnormal structure. However,most cases of ED are associated with vascular diseases. An erectioncannot be sustained without sufficient blood flow into and entrapmentwithin the erectile bodies of the penis, and vascular related ED can bedue to a malfunction of either the arterial or the venous system.

In a healthy individual, penile erection is generated by increased bloodlow into the penis via arterial dilation and decreased blood flow fromthe penis via venous occlusion. Arterial dilation is generated byactivation of the cavernous nerve (a parasympathetic nerve), whichcauses relaxation of corporeal smooth muscle of the cavernosal andtrabecular spaces. Penile erection begins with the filling and expansionof the three erectile bodies: the corpus spongiosum and the two corporacavernosa. This expansion compresses the venules, preventing blood fromleaving the penis and furthering the erection.

Persons with vasculogenic erectile dysfunction are unable to achievepenile erection due to either insufficient arterial blood flow orinsufficient venous occlusion or both. Normal reflex erectioncoordinates dilation of penile blood vessels, augmenting vascularfilling, and venous occlusion, preventing leakage and increasing penilestiffness.

Stimulation of a target nerve N, such as the dorsal nerve of the penis(DNP) afferents activates spinal circuitry that coordinates efferentactivity in the cavernous nerve (CN), increasing filling via dilation ofpenile arteries, and efferent activity in the pudendal nerve (PN),preventing leakage via occlusion of penile veins, producing a sustainedreflex erection (see FIG. 1).

FIGS. 2 and 3 show a profile and cross-section of the penis,illustrating the anatomical relationship of the erectile tissue (corporacavernosa and corpus spongiosum) inside the penis. FIGS. 4 and 5 showthe physiological changes in the size of the penile arteries, erectiletissue, and veins during erection. FIG. 4 shows the penile arteriesconstricted, the erectile tissue collapsed, and the veins open prior toan erection. Arterial dilation leads to increased inflow of blood, whichfills and expands the erectile tissue as the veins are compressed todecrease outflow of blood from the erectile tissue, as shown in FIG. 5.

III. Methods of Treatment For ED

Methods of treatment for erectile dysfunction are available but areeither often discontinued due to loss of efficacy or side effects orreserved as a final recourse requiring irrevocable damage. Three linesof treatment exist for ED. Oral therapy (PDE-5 inhibitors) is usuallythe first line of treatment, and it can be effective in up to 70% of menwhen it is first administered, but half of the patients stop takingPDE-5 inhibitors because they lose their effectiveness within one tothree years. The second line of treatment is usually a minimallyinvasive therapy such as a vacuum device or direct administration of avasoactive agent. The second-line treatments are usually effective in33% to 70% of men, but they are also later discontinued by over half ofthe patients, often due to side effects such as pain or local damage atthe site of administration. For the 30% to 65% of men who fail ordiscontinue oral therapy, the total cost for the second line oftreatment (vacuum device or alprostadil, administered via injection ortransurethrally) would be $1 to $6 billion. However, side effects ofpain and local damage are associated with the second line of treatment,and at least half of the men discontinue this form of therapy. If themen who failed or discontinued both the first and second lines oftreatment chose to receive a penile prosthesis, the total cost would beover $20 billion. Yet, implantation of a penile prosthesis is reservedfor the final method of treatment because the implantation causespermanent (irrevocable) damage to the erectile tissue resulting in theloss of any future erection if the implant is removed. Thus, analternative approach is needed that can provide a multitude ofadvantages over the current therapies.

IV. Neuromodulation Stimulation to Evoke Erection

Systemic side effects (headache, flushing, dyspepsia, etc.) andpermanent damage to the corpora cavernosa may be avoided by electricallystimulating a peripheral nerve to activate a reflex that coordinatesarterial dilation with venous occlusion, producing an erection. Inanesthetized, spinalized rats, electrical stimulation of afferentpathways in the dorsal nerve of the penis (DNP) can produce an increasein corpus cavernous pressure (CCP). The increase in CCP is gated to theonset and offset of stimulation and has been sustained for up to fifteenminutes. Previous results in the dog demonstrated that reflex erectionsare repeatable for a period of three to five hours. Stimulation of theDNP leads to transient increases in the EMG activity of theischiocavernosus (IC) and bulbospongiosus (BS) muscles, which areresponsible for venous occlusion. Venous occlusion prevents leakage ofblood from the penis and explains why DNP stimulation can evokesupra-systolic increases in penile pressure. These animal experimentsdemonstrate that DNP stimulation can evoke a reflex erection, but theydo not determine if the reflex erection is comparable to the erectionsevoked by the present treatment methods.

An implantable stimulation system is needed that can provide an erectionquickly and is acceptable to men who use or may need to use nitrates totreat cardiovascular disease because over 35% of men with cardiovasculardisease develop ED. The loss of efficacy of oral therapy is likely dueto the long duration (four to eighteen hours) of action, and theconsistently elevated drug concentrations can reduce the response to thedrug via tachyphylaxis or increased tolerance as seen with nitroglycerintolerance. No loss of efficacy is expected with an implantablestimulation system that will only be activated five minutes before andduring erection, and it will provide controlled release ofneurotransmitter via activation of a reflex in the central-nervoussystem.

The implantable stimulation system may be activated by the movement of amagnet over a magnetic reed switch within the implantable pulsegenerator of the stimulation system, or the press of a remote button,for example. Unlike the second line of treatment, this approach will notrequire a constrictive ring, needle insertion, or urethral-suppositoryinsertion, which can cause local injury prior to each erection and leadto discontinuation of treatment. In contrast to the penile implant, animplantable stimulation system approach will not damage the erectiletissue.

There remains a need for systems and methods that can effectivelyrestore sexual function, in a straightforward manner, without requiringdrug therapy and complicated (and in some instanced irrevocable)surgical procedures.

SUMMARY OF THE INVENTION

The implantable stimulation system will use electrical stimulation ofthe dorsal genital nerve of either the male or the female to provide asexual restoration function on-demand with a simple surgical procedurethat preserves the existing anatomy, wherein the sexual restoration mayinclude erection, ejaculation, arousal (engorgement), and lubrication,as non-limiting examples.

One aspect of the invention provides systems and methods for thetreatment of sexual dysfunction by the stimulation of the left and/orright branches of the dorsal genital nerves using a stimulationelectrode sized and configured to be implanted in tissue in a region ator near a pubic symphysis, and an implantable pulse generator to conveyelectrical stimulation waveforms to the stimulation electrode tostimulate the left branch and/or the right branch of the dorsal genitalnerves.

The stimulation waveforms conveyed to the stimulation electrode affectafferent stimulation of the left and/or right branches of the dorsalgenital nerves, the afferent stimulation activating spinal circuitrythat coordinates efferent activity in the cavernous nerve and efferentactivity in the pudendal nerve, producing a sexual function. Theelectrical stimulation waveform includes at least a variable frequencycomponent and/or a variable duty cycle component and/or a variableamplitude component and/or a variable pause component to ward offhabituation. For example, the electrical stimulation waveform mayinclude a variable frequency in the range of about one Hz to aboutfifteen Hz, and a variable amplitude in the range of about 100 microampsto about 20 milliamps, and a variable duty cycle in the range of aboutzero seconds to about ten seconds, and a variable pause component in therange of about zero seconds to about ten seconds.

The stimulation electrode may be sized and configured to be implanted inadipose tissue. The stimulation electrode may comprise an elongated leadsized and configured to be implanted within the adipose tissue region,the lead including at least two electrically conductive portions toapply electrical stimulation to nerve tissue in the adipose tissueregion, and at least two expandable anchoring structures deployable fromthe lead to engage adipose tissue and resist dislodgment and/ormigration of the at least two electrically conductive portions withinthe adipose tissue region.

An additional aspect of the invention provides systems and methods forthe treatment of sexual dysfunction by implanting at least onestimulation electrode in tissue at or near a pubic symphysis, andapplying stimulation waveforms to the at least one stimulation electrodeto achieve stimulation of left and/or right branches of the dorsalgenital nerves.

A single stimulation electrode may be implanted, wherein applying thestimulation waveforms achieves bilateral stimulation of the left andright branches of the genital dorsal nerves.

Alternatively, at least a first stimulation electrode and a secondstimulation electrode may be implanted. In this configuration, thestimulation waveforms conveyed to the at least a first stimulationelectrode affect stimulation of the left and/or right branches of thedorsal genital nerves, and the stimulation waveforms conveyed to the atleast a second stimulation electrode affect stimulation of the leftand/or right branches of the dorsal genital nerves.

Other features and advantages of the inventions are set forth in thefollowing specification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the stimulation of a target afferent nerveand the spinal circuitry activated to coordinate efferent nerve activityfor sexual restoration.

FIG. 2 is a lateral cross-sectional view of a penis, showing therelationship of the erectile tissue inside the penis.

FIG. 3 is an end section view of the penis taken generally along line3-3 of FIG. 2.

FIG. 4 is a side sectional view of penile tissue prior to an erection.

FIG. 5 is a side sectional view of penile tissue as shown in FIG. 4,showing the changes in the penile tissue causing an erection.

FIG. 6 is a view of a stimulation assembly that provides electricalstimulation to central nervous system tissue, muscles and/or nervesinside the body using a general purpose implantable pulse generator.

FIGS. 7A and 7B are front and side views of the general purposeimplantable pulse generator shown in FIG. 6, which is powered by aprimary battery.

FIGS. 8A and 8B are anterior anatomic views of the system shown in FIG.6 after implantation in an adipose tissue region at or near near thepubic symphysis.

FIG. 8C is an anterior anatomic view of an alternative configuration ofthe system shown in FIG. 8B, showing more than one lead and electrodeimplanted in the targeted tissue region.

FIG. 9 is an anterior anatomic view of the pelvic girdle in a human.

FIG. 10 is a lateral section view of the pelvic girdle region shown inFIG. 9.

FIG. 11 is an inferior view of a female pelvic girdle region.

FIG. 12 is an anatomic view showing the implantable pulse generatorshown in FIGS. 7A and 7B in association with an external programmer thatrelies upon wireless telemetry, and showing the programmer's capabilityof communicating with the implantable pulse generator up to an arm'slength away from the implantable pulse generator.

FIG. 13 is a system view of an implantable pulse generator systemincorporating a clinician programmer derivative and showing the system'scapability of communicating and transferring data over a network,including a remote network.

FIG. 14 is a perspective graphical view of one possible type of patientcontroller that may be used with the implantable pulse generator shownin FIGS. 7A and 7B.

FIG. 15 is a block diagram of a circuit that the implantable pulsegenerator shown in FIGS. 7A and 7B can incorporate.

FIG. 16 is a circuit diagram showing a possible circuit for the wirelesstelemetry feature used with the implantable pulse generator shown inFIGS. 7A and 7B.

FIG. 17 is a circuit diagram showing a possible circuit for the stimulusoutput stage and output multiplexing features used with the implantablepulse generator shown in FIGS. 7A and 7B.

FIG. 18 is a graphical view of a desirable biphasic stimulus pulseoutput of the implantable pulse generator for use with the system shownin FIG. 6.

FIG. 19 is a circuit diagram showing a possible circuit for themicrocontroller used with the implantable pulse generator shown in FIGS.7A and 7B.

FIG. 20 is a circuit diagram showing one possible option for a powermanagement sub-circuit where the sub-circuit includes MOSFET isolationbetween the battery and charger circuit (when used), the powermanagement sub-circuit being a part of the implantable pulse generatorcircuit shown in FIG. 6.

FIG. 21 is a circuit diagram showing a second possible option for apower management sub-circuit where the sub-circuit does not includeMOSFET isolation between the battery and charger circuit (when used),the power management sub-circuit being a part of the implantable pulsegenerator circuit shown in FIG. 6.

FIG. 22 is a circuit diagram showing a possible circuit for the VHHpower supply feature used with the implantable pulse generator shown inFIGS. 7A and 7B.

FIGS. 23 and 24 are anatomic section views of the adipose tissue regionwith one lead and electrode associated with the system shown in FIG. 6,after having been implanted.

FIGS. 25A and 25B are perspective views of the lead and electrodeassociated with the system shown in FIG. 6.

FIG. 26 is a side interior view of a representative embodiment of a leadof the type shown in FIGS. 23 and 24.

FIG. 27 is an end section view of the lead taken generally along line27-27 in FIG. 26.

FIG. 28 is an elevation view, in section, of a lead and electrode of thetype shown in FIGS. 23 and 24 residing within an introducer sheath forimplantation in a targeted tissue region, the anchoring members beingshown retracted within the sheath.

FIG. 29 is a perspective view of a molded cuff electrode prior toimplantation.

FIG. 30 is a perspective view of an alternative embodiment of the moldedcuff electrode shown in FIG. 29, showing the lead extending generallyparallel from the cuff electrode.

FIGS. 31 and 32 are plan views showing both solid and segmentedembodiments for the electrically conductive surface.

FIG. 33 is a perspective, diagrammatic view of the molded cuff electrodeshown in FIG. 29 implanted about a nerve and coupled to a pulsegenerator to deliver a neuromodular stimulation to achieve a desiredtherapeutic result.

FIG. 34 is a side section view of the molded cuff electrode takengenerally along line 34-34 on FIG. 33.

FIG. 35 is a plan view of an alternative embodiment of the conductivesurfaces configuration.

FIG. 36 is a side section view of the alternative embodiment shown inFIG. 35 positioned about a nerve N.

FIG. 37 is an applicator tool for placement of a molded cuff electrodeof the type shown in FIG. 29 about a nerve, the applicator tool beingshown before mounting of the electrode with the electrode deliverymechanism in an aft condition.

FIG. 38 is a side view of the applicator tool shown in FIG. 37, with theelectrode mounted and the electrode delivery mechanism in an aftcondition, ready to implant the electrode about a nerve.

FIG. 39 is a side view of the applicator tool shown in FIG. 37, with theelectrode delivery mechanism translated to a forward condition toimplant the electrode about a nerve.

FIG. 40 is a plane view of a system of surgical tools that can be use toimplant the system shown in FIG. 6.

FIGS. 41 through 44 illustrate general steps of implanting the systemshown in FIG. 6 in either a single surgical procedure or two surgicalprocedures.

The invention may be embodied in several forms without departing fromits spirit or essential characteristics. The scope of the invention isdefined in the appended claims, rather than in the specific descriptionpreceding them. All embodiments that fall within the meaning and rangeof equivalency of the claims are therefore intended to be embraced bythe claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The various aspects of the invention will be described in connectionwith the restoration of sexual function (e.g., erectile restoration) bythe unilateral or bilateral stimulation of the left and/or rightbranches of the dorsal genital nerves using a lead or leads implanted inadipose or other tissue in the region at or near the pubic symphysis, orelectrode(s) implanted on the left and/or right branches of the dorsalgenital nerves. That is because the features and advantages of theinvention are well suited for this purpose. Still, it should beappreciated that the various aspects of the invention can be applied inother forms and in other locations in the body to achieve otherobjectives as well. These objectives pertain to both male and female,human and animal, and may include, but are not limited to, erection,ejaculation, arousal, and lubrication.

I. System Overview

A. Neuromodulation Stimulation

Afferent stimulation produces a full penile erection by activatingsensory fibers with a stimulation pattern that mimics the pattern ofsensory signals sent to reflex circuitry during coitus. The reflexcircuitry then coordinates the 1) increase in blood flow into the penisvia dilation of penile arteries with the 2) decrease in blood flowexiting the penis via occlusion of penile veins (see FIG. 1).

The afferent pathway(s) may be activated by stimulation of any genitalnerve including the dorsal penile nerve; the ilioinguinal nerve; themedial, lateral, and posterior scrotal branches of the perineal nerve;the cavernous nerve, the perineal branch of the posterior femoralcutaneous nerve, the dorsal clitoral nerve, the vaginal nerves, and thelabial nerves, for example. These pathways may also be activated bystimulation of any spinal root which supplies any of these genitalnerves. Any combination of the genital nerves and/or their spinal rootswill be referred to as the target nerve N.

An implant system 10 will be used to provide electrical stimulation of atarget nerve N (e.g., the dorsal nerve of the penis) to providesustainable erections on-demand with a simple surgical procedure thatpreserves the existing anatomy.

The electrical stimulation may be applied with any type of electricalcontact such as a lead 12 placed in, on, around, or near any of thetarget nerve N named above. Note that the electrode 16 may be in contactwith the target nerve N, or it may be some distance (on the order ofcentimeters) away because it does not have to be in contact with thetarget nerve N to activate it.

Stimulation may be applied through a lead, such as a fine wireelectrode, inserted via needle introducer in proximity of a target nerveN. When proper placement is confirmed, as indicated by patient sensationor visible movement of related organs, such as the penis, scrotum, oranal sphincter, (or clitoris for women), the needle may be withdrawn,leaving the electrode in place.

Alternatively, stimulation may be applied through any type of nerve cuff(spiral, helical, cylindrical, book, flat interface nerve electrode(FINE), slowly closing FINE, etc.) that is surgically placed on oraround a target nerve N.

Stimulation may also be applied through a penetrating electrode, such asan electrode array that is comprised of any number (>1) of needle-likeelectrodes that are inserted into a target nerve N.

In all cases, the lead 12 may be routed subcutaneously to an implantablepulse generator (IPG) 18. The IPG may be located some distance from theelectrode 16 or it may be integrated with the electrode, eliminating theneed to route the lead 12 subcutaneously.

Control of the stimulation parameters may be provided by an externalcontroller. The IPG external controller (clinician programmer 36) may bea remote unit that uses wireless communication (such as RF or magneticsignals) to control the IPG 18. The implantable pulse generator 18 mayuse regulated voltage (10 mV to 20 V), regulated current (10 μA to 50mA), and/or passive charge recovery to generate the stimulationwaveform.

The pulse may by monophasic or biphasic. In the case of the biphasicpulse, the pulse may be symmetrical or asymmetrical. Its shape may berectangular or exponential or a combination of rectangular andexponential waveforms. The pulse width of each phase may range between10 μsec and 10 to the sixth power μsec.

Pulses may be applied in continuous or intermittent trains (i.e. thestimulus frequency changes as a function of time). In the case ofintermittent pulses, the on/off duty cycle of pulses may be symmetricalor asymmetrical, and the duty cycle may be regular and repeatable fromone intermittent burst to the next or the duty cycle of each set ofbursts may vary in a random (or pseudo random) fashion. Varying thestimulus frequency and/or duty cycle may assist in warding offhabituation because of the stimulus modulation.

The stimulating frequency may range from 1 to 300 Hz, and the frequencyof stimulation may be constant or varying. In the case of applyingstimulation with varying frequencies, the frequencies may vary in aconsistent and repeatable pattern or in a random (or pseudo random)fashion or a combination of repeatable and random patterns.

B. The Implant System

FIG. 6 shows an implant system 10 for the restoration of sexual functionin animals, including humans.

The system 10 includes an implantable lead 12 having a proximal anddistal end coupled to an implantable pulse generator or IPG 18. The lead12 and the implantable pulse generator 18 are shown implanted within atissue region T of a human or animal body.

The distal end of the lead 12 includes at least one electricallyconductive surface, which will in shorthand be called an electrode 16.The electrode 16 is implanted in electrical conductive contact with atleast one functional grouping of neural tissue, muscle, or at least onenerve, or at least one muscle and nerve. The implantable pulse generator18 includes a connection header 14 that desirably carries a plug-inreceptacle (connector) for the lead 12. In this way, the lead 12electrically connects the electrode 16 to the implantable pulsegenerator 18.

The implantable pulse generator 18 is sized and configured to beimplanted subcutaneously in tissue, desirably in a subcutaneous pocketP, which can be remote from the electrode 16, as FIG. 6 shows.Desirably, the implantable pulse generator 18 is sized and configured tobe implanted using a minimally invasive surgical procedure.

The lead 12 and electrode 16 are sized and configured to be implantedpercutaneously in tissue, and to be tolerated by an individual duringextended use without pain or discomfort. The comfort is both in terms ofthe individual's sensory perception of the electrical waveforms that theelectrode applies, as well as the individual's sensory perception of thephysical presence of the electrode and lead. In both categories, thelead 12 and electrode 16 are desirably “imperceptible.”

In particular, one configuration of the lead 12 and electrode 16 aresized and configured to reside with stability in soft or adipose tissuein the lower anterior pelvic region of the body (see FIGS. 8A and 8B).It has been discovered that, when properly placed in this region, one ormore lead/electrode(s) 16 are uniquely able to deliver electricalstimulation current simultaneously to both left and right branches ofthe dorsal genital nerves, present near the clitoris in a female andnear the base of the penis of a male (see FIGS. 8A and 8B). Specificfeatures of the lead 12 and electrode 16 that make them well suited forthis purpose, as well as other purposes, will be described in greaterdetail later.

As FIGS. 7A and 7B show, the implantable pulse generator 18 includes acircuit 20 that generates electrical stimulation waveforms. An on-board,primary battery 22 desirably provides the power. The implantable pulsegenerator 18 also desirably includes an on-board, programmablemicrocontroller 24, which carries embedded code. The code expressespre-programmed rules or algorithms under which the desired electricalstimulation waveforms are generated by the circuit 20. The implantablepulse generator 18 may also include an electrically conductive case 26,which can also serve as the return electrode for the stimulus currentintroduced by the lead/electrode when operated in a monopolarconfiguration.

As shown in FIGS. 8A and 8B, the implantation site can comprise a tissueregion on the posterior hip. Alternatively, the implantation site cancomprise a more medial tissue region in the lower abdomen. There, thepulse generator 18 can reside for extended use without causing painand/or discomfort and/or without effecting body image.

The implant system 10 includes an external patient controller 37 (seeFIGS. 8A and 14). The patient controller 37 is sized and configured tobe held or worn by the individual to transcutaneously activate anddeactivate or modify the output of the pulse generator 18. The patientcontroller 37 may, e.g., be a simple magnet that, when placed near thesite where the pulse generator 18 is implanted (see FIG. 14), toggles amagnetic switch within the implantable pulse generator 18 between an oncondition and an off condition, or advances through a sequence ofalternative stimulus modes pre-programmed by the clinician into theimplantable pulse generator 18. Alternatively, the patient controller 37may comprise more sophisticated circuitry that would allow theindividual to make these selections through an RF field (magnetic and/orelectric) that passes through the skin and tissue within an arm's lengthdistance (or up to two meters) from the implanted pulse generator 18.

According to its programmed rules, when switched on, the implantablepulse generator 18 generates prescribed stimulation waveforms throughthe lead 12 and to the electrode 16. These waveforms bilaterallystimulate the left and right branches of the dorsal genital nerves in amanner that achieves the desired physiologic response.

It has been discovered that bilateral stimulation of the dorsal genitalnerves achieved by placement of a single electrode 16 at a uniquelocation in the body (which will be described in greater detail later),achieves the desired physiologic result. Alternatively, more than oneelectrode may be placed to stimulate the dorsal genital nerves (e.g.,one or more electrodes to stimulate the left branch and one or moreelectrodes to stimulate the right branch, see FIG. 8C). Bilateralstimulation may be achieved with a single electrode 16, but due toanatomical variations in the patient or possible target nerve N damageprior to and unrelated to implantation, the patient may be limited tounilateral stimulation of either the left or the right branches of thedorsal genital nerve, for example. Or, the physician may not be able toimplant only one electrode 16 that can activate both branches of thedorsal genital nerve, but if both branches are healthy, then thephysician will likely want to stimulate both branches. In this case thephysician will implant two or more electrodes 16, one on, in, or nearthe left branch of the dorsal genital nerve and one on, in, or near theright branch of the dorsal genital nerve.

Using the controller 26, the individual may turn on or turn off thesexual restoration control waveforms at will or adjust the waveforms toachieve the desired functional restoration result. As previouslydiscussed, erectile restoration is just one example of a functionalrestoration result. Additional examples of desirable therapeutic(treatment) or functional restoration indications will be described ingreater detail in section “V. Representative Indications.”

The system 10 desirably includes means for selectively varying thefrequency or range of frequencies for a variable duration at which thestimulation waveforms are applied by the one or more electrodes 18. Bymodulating the frequency and/or duration of the stimulation waveform,the same system components and placement of electrodes can serve toachieve markedly different physiologic responses, and in addition,reduce habituation.

The shape of the waveform can vary as well. It can, e.g., be a typicalsquare pulse, or possess a ramped shape. The pulse, or the rising orfalling edges of the pulse, can present various linear, exponential,hyperbolic, or quasi-trapezoidal shapes. The stimulation waveform can becontinuous, or it can be variable and change cyclically or in stepfashion in magnitude and waveform over time.

In a non-limiting exemplary embodiment, the stimulus waveforms mayinclude a variable frequency for a variable duration (e.g., a firststimulation at 5 Hz for 2 seconds, then 7 Hz for 3 seconds, then 6-Hzfor 1 second, and so on), intermittent stimulation (apply stimulation inbursts separated by pauses in stimulation (e.g., stimulation for 3seconds, rest for 2 seconds, repeat, and so on). The stimulus waveformsmay also include a continuously or intermittently applied duty cycle ofpulses. This may be considered the same as changing the frequency but italso refers to 1) the duration of bursts of stimulation and 2) theduration of pauses between the bursts. For example, a variable dutycycle for intermittent pulses may include stimulation with 10 pulses,then off for 500 milliseconds, stimulation with 15 pulses, then off for750 milliseconds, stimulation with 5 pulses, then off for 2 seconds, andit could keep going in this variable pattern.

The stimulus waveforms may also include stimulation at differentamplitudes. This may be beneficial because increasing the amplitude mayincrease penile tumescence to a certain degree, and then increasing theamplitude further may be used to cause ejaculation. Thus, amplitudemodulation may be used to control the response. Varying the amplitudemay also provide another form of anti-habituation control, allowing asexual function (e.g., erection) to remain more robust than if thetarget nerve N was stimulated at a constant amplitude. Amplitudemodulation may also more realistically recreate the varying level offiber activation that occurs during coitus.

The patient controller 37 and/or a clinician programmer, for example,may include a manual-actuated switch or control knob which an operatoroperates or tunes to acquire a desired waveform frequency, given thedesired physiologic response.

C. The Anatomic Landmarks

As already described, certain components of the implant system 10 aresized and configured to be implanted in adipose tissue in the loweranterior pelvic region, where it has been discovered that effectivebilateral stimulation of both the left and right branches of the dorsalgenital nerves can be achieved with one or more electrodes. The mainanatomic landmark guiding the unique placement of these components isthe pubic symphysis.

As FIG. 9 shows, the hip bones are two large, irregularly shaped bones,each of which develops from the fusion of three bones, the ilium,ischium, and pubis. The ilium is the superior, fan-shaped part of thehip bone. The ala of the ilium represents the spread of the fan. Theiliac crest represents the rim of the fan. It has a curve that followsthe contour of the ala between the anterior and posterior superior iliacspines.

As FIGS. 9 and 10 show, the sacrum is formed by the fusion of fiveoriginally separate sacral vertebrae. The hip bones are joined at thepubic symphysis anteriorly and to the sacrum posteriorly to form thepelvic girdle (see FIG. 9). The pelvic girdle is attached to the lowerlimbs. Located within the pelvic girdle are the abdominal viscera (e.g.,the ileum and sigmoid colon) and the pelvic viscera (e.g., the urinarybladder and prostate gland for males, and the urinary bladder andreproductive organs such as the uterus and ovaries for females).

Within this bony frame (see FIGS. 9 and 10), the pudendal nerve isderived at the sacral plexus from the anterior divisions of the ventralrami of S2 through S4 and carries afferent (sensory) and efferent(motor) nerve components that innervate muscles and organs in the lowerabdomen. The pudendal nerve extends bilaterally, in separate branches onleft and right sides of the pelvic girdle. Each branch accompanies theinterior pudendal artery and leaves the pelvis through the left andright greater sciatic foramens between the piriformis and coccygeusmuscles. The branches hook around the ischial spine and sacrospinousligament and enter the skin and muscles of the perineum through the leftand right lesser sciatic foramen.

The Figures are largely based upon the anatomy of a male, but the partsof the male perineum are homologues of the female. As shown in FIG. 11,which is based on the anatomy of a female, the bilateral left and rightbranches extend anteriorly through the perineum, each ending as thedorsal genital nerve of the penis or clitoris. The genital nerves arethe chief sensory nerve of the external genitalia.

As FIG. 11 shows, in the female and male, adipose tissue overlays thepubic symphysis. The bilateral branches of the genital nerves innervatethis tissue region. In the female, this tissue region is known as themons pubis. In the male, the penis and scrotum extend from this region.Further discussion regarding the fixation of the lead 12 and electrode16 in adipose tissue will be described later.

D. Conditions Required to Evoke Erection

Erection is a complex process involving control from the autonomic andsomatic nervous systems. There are two peripheral neural pathways thatcontrol erection in cats and dogs. The parasympathetic pathway (S2-S4)mediates tactile, as well as psychically induced erection, while thesympathetic pathway (T10-L2) mediates only psychically induced erection.Although erection involves many central and psychogenic factors, reflexerections are mediated by a spinal mechanism, and do not requireparticipation of supraspinal structures.

The implant system 10 will focus on spinally-mediated reflex erection,as this is most relevant to restoration of sexual function. Theafferents of the erection reflex arises from the dorsal nerve of thepenis (DNP), while the efferent side includes both the cavernous andpudendal nerves (see FIG. 1). The cavernous nerve mediates engorgementof the penis as a result of dilation of penile blood vessels (mediatedby a non-adrenergic non-cholinergic mechanism, putatively nitric oxide),and venous occlusion may also play a role in engorgement. The pudendalnerve carries the somatic innervation of the bulbospongiosus whichserves to further increase cavernous pressure and penile stiffness, andthe ischiocavernosus which can also augment stiffness of the penis.

Previous studies indicate that electrical stimulation of the dorsalnerve of the penis can evoke reflex penile erection before and after T8spinal cord transection in the rat. In the spinalized rat, DNPstimulation produces a copulatory-like reflex, including erectile andejaculatory responses. DNP stimulation evokes central reflexes withlatencies of 50 milliseconds to 150 milliseconds and is thought tomediate reflex erection. Stimulus frequencies of two Hz to ten Hz havebeen successful in eliciting reflex erections before and afterspinalization, and spinalization increases the combination of stimulusparameters that are successful in evoking erection.

Low amplitude genital nerve stimulation is not expected to cause painbecause it has been observed that low amplitude (5±3 mA), low frequency(10 Hz) electrical stimulation of the dorsal genital (clitoral) nervecreated a sensation that was well tolerated by all women (n=17), oftendescribed as a thumping (24%), buzzing (18%), or pulsing (12%)sensation, and the amplitude could be increased to almost double (9+3mA) before it became uncomfortable.

The implant system 10 is sized and configured to evoke a rigid erectionand sustain an erection for about 30 minutes that is comparable inboth 1) corpus cavernous pressure (CCP) and 2) CCP/BP (blood pressure)to the erection produced by intracavernous injection of alprostadil. Arigid erection is defined by CCP≧BP and a functional score of 4 or 5(sufficient for sexual intercourse or full erection) on the Schramekgrading system. The time to erection once the implant system 10 isturned on may be in the range of a few minutes (e.g., two to tenminutes). When the implant system is turned off, the erection willsubside comparable to a normal healthy response.

E. Afferent and Efferent Stimulation

The system and methods described for afferent stimulation can provide amore rigid and longer lasting erection than methods that use efferentstimulation because afferent stimulation activates a reflex thatcoordinates the increase of filling via dilation of penile arteries withthe prevention of leakage via occlusion of penile veins. Presentstimulation methods do not stimulate both cavernous and pudendal nerves(or nerve branches), nor do present stimulation methods use reflexes tocoordinate the individual processes involved in erection. Specifically,afferent stimulation can 1) provide a longer lasting erection because itactivates a reflex that controls the rate and amount of neurotransmitterreleased from the cavernous nerve. On the other hand, direct efferentstimulation of the cavernous nerve can release excessive amounts ofneurotransmitter. The reflex activated by afferent stimulation also 2)coordinates efferent activity in the pudendal nerve to prevent leakageof blood from the penis via occlusion of penile veins, whereas efferentstimulation of the cavernous nerve does nothing to prevent leakage ofblood from the penis

Additionally, efferent stimulation risks generating the perception ofpain due to the current amplitude that may be required. Afferentstimulation may avoid the generation of pain because lower amplitudes ofcurrent can be used to activate selectively the large sensory fiberswithout activating the smaller C-fibers that transmit signals to paincenters.

Nevertheless, a coordinated stimulation to both afferent and efferentnerves, or efferent and efferent nerves, including coordinatedstimulation of both the cavernous and pudendal nerves (or branches), mayalso be used to produce the desired functional result.

II. Details of Implant System

A. The Implantable Pulse Generator

As previously described, FIG. 6 shows a system 10 for the functionalrestoration of sexual function. The assembly includes an implantablelead 12 and electrode 16 coupled to an implantable pulse generator orIPG 18. The lead 12 and the implantable pulse generator 18 are shownimplanted within a tissue region T of a human or animal body.

Desirably, the components of the implantable pulse generator 18 aresized and configured so that they can accommodate several differentindications, without major change or modification (see FIG. 7A).Examples of components that desirably remain unchanged for differentindications include the case 26, the battery 22, the microcontroller 24,much of the software (firmware) of the embedded code, the powermanagement circuitry 40, and the stimulus power supply, both of whichare part of the circuitry 20. Thus, a new indication may require onlychanges to the programming of the microcontroller 24. Most desirably,the particular code is remotely embedded in the microcontroller 24 afterfinal assembly, packaging, and sterilization of the implantable pulsegenerator 18.

Certain components of the implantable pulse generator 18 may be expectedto change as the indication changes; for example, due to differences inleads and electrodes, the connection header 14 and associatedreceptacle(s) for the lead may be configured differently for differentindications. Other aspects of the circuit 20 may also be modified toaccommodate a different indication; for example, the stimulator outputstage(s), sensor(s) and/or sensor interface circuitry.

In this way, the implantable pulse generator 18 accommodates implantingin diverse tissue regions and also accommodates coupling to a lead 12and an electrode 16 having diverse forms and configurations, againdepending upon the therapeutic or functional effects desired. For thisreason, the implantable pulse generator can be considered to be generalpurpose or “universal.”

1. Desirable Technical Features

The implantable pulse generator 18 can incorporate various technicalfeatures to enhance its universality.

a. Small, Composite Case

According to one desirable technical feature, the implantable pulsegenerator 18 can be sized small enough to be implanted (or replaced)with only local anesthesia. As FIGS. 7A and 7B show, the functionalelements of the implantable pulse generator 18 (e.g., circuit 20, themicrocontroller 24, the battery 22, and the connection header 14) areintegrated into a small, composite case 26. As can be seen in FIGS. 2Aand 2B, the implantable pulse generator 18 may comprise a case 26 havinga small cross section, e.g., (5 mm to 15 mm thick)×(45 mm to 60 mmwide)×(45 mm to 60 mm long). The overall weight of the implantable pulsegenerator 18 may be approximately twenty to thirty grams. Thesedimensions make possible implantation of the case 26 with a smallincision; i.e., suitable for minimally invasive implantation.Additionally, a smaller or larger, but similarly shaped IPG might berequired for other applications, such as with more stimulus channels(thus requiring a large connection header) and/or a smaller or largerinternal battery.

The case 26 of the implantable pulse generator 18 is desirably shapedwith a smaller end 30 and a larger end 32. As FIG. 6 shows, thisgeometry allows the smaller end 30 of the case 26 to be placed into theskin pocket P first, with the larger end 32 being pushed in last.

Desirably, the case 26 for the implantable pulse generator 18 comprisesa laser welded implant grade titanium material. This construction offershigh reliability with a low manufacturing cost. The clam shellconstruction has two stamped or successively drawn titanium case halvesthat are laser welded around the circuit assembly and battery 22 withfeed-thrus. Typically, a molded plastic spacing nest is used to hold thebattery 22, the circuit 20, and perhaps a power recovery (receive) coil(if a rechargeable battery is used) together and secure them within thehermetically sealed titanium case. An implantable pulse generator havinga rechargeable battery can be used of the type described in copendingU.S. patent application Ser. No. 11/150,418, filed 10 Jun. 2005 andentitled “Implantable Pulse Generator for Providing Functional and/orTherapeutic Stimulation of Muscles and/or Nerves and/or Central NervousSystem Tissue,” which is incorporated herein by reference. Theelectronics may be fabricated on a flexible or flex-rigid PC board usingvery high density technique include adhesive flip-chip or chip-on-boardmounting of the larger semiconductor devices. The tissue contactmaterials used in the manufacture of the IPG may all have Master Fileswith FDA demonstrating their biocompatibility.

The implantable pulse generator 18 shown in FIGS. 7A and 7B includes aclam-shell case 26 having a thickness that is selected to provideadequate mechanical strength The implantable pulse generator 18 may beimplanted at a target implant depth of not less than five millimetersbeneath the skin, and not more than fifteen millimeters beneath theskin, although this implant depth may change due to the particularapplication, or the implant depth may change over time based on physicalconditions of the patient.

b. Primary Power Source

According to one desirable technical feature, the implantable pulsegenerator 18 desirably possesses an internal battery capacity sufficientto allow a service life of greater than three years with the stimulusbeing a high duty cycle, e.g., virtually continuous, low frequency, lowcurrent stimulus pulses, or alternatively, the stimulus being higherfrequency and amplitude stimulus pulses that are used onlyintermittently, e.g., a very low duty cycle.

To achieve this feature, the primary battery 22 of the implantable pulsegenerator 18 desirably comprises a primary power source; most desirablyan implant grade Lithium Ion battery 22. Given the average quiescentoperating current (estimated at 8 μA plus 35 μA for a wireless telemetryreceiver pulsing on twice every second) and a seventy percent efficiencyof the stimulus power supply, a 1.0 Amp-hr primary cell battery canprovide a service life of less than two years, which is too short to beclinically or commercially viable for this indication. Therefore, theimplantable pulse generator 18 desirably incorporates a primary battery,e.g., a Lithium Ion battery. Given representative desirable stimulationparameters (which will be described later), a Lithium Ion battery with acapacity of at least 30 mA-hr will operate for over three years. LithiumIon implant grade batteries are available from a domestic supplier. Arepresentative battery provides 35 mA-hr in a package configuration thatis of appropriate size and shape to fit within the implantable pulsegenerator 18.

The implantable pulse generator 18 desirably incorporates circuitryand/or programming to assure that the implantable pulse generator 18will suspend stimulation, and perhaps fall-back to only very low ratetelemetry, and eventually suspends all operations when the primarybattery 22 has discharged the majority of its capacity (i.e., only asafety margin charge remains). Once in this dormant mode, theimplantable pulse generator may provide limited communications and is incondition for replacement.

c. Wireless Telemetry

According to one desirable technical feature, the system or assembly 10includes an implantable pulse generator 18, which desirably incorporateswireless telemetry (rather that an inductively coupled telemetry) for avariety of functions to be performed within arm's reach of the patient,the functions including receipt of programming and clinical parametersand settings from the clinician programmer 36, communicating usagehistory to the clinician programmer, and providing user control of theimplantable pulse generator 18. Each implantable pulse generator mayalso have a unique signature that limits communication to only thededicated controllers (e.g., the matched patient controller, or aclinician programmer configured for the implantable pulse generator inquestion).

The implantable pulse generator 18 desirably incorporates wirelesstelemetry as an element of the implantable pulse generator circuit 20shown in FIG. 15. A circuit diagram showing a desired configuration forthe wireless telemetry feature is shown in FIG. 16. It is to beappreciated that modifications to this circuit diagram configurationwhich produce the same or similar functions as described are within thescope of the invention.

As shown in FIG. 12, the assembly 10 desirably includes a clinicianprogrammer 36 that, through a wireless telemetry 38, transfers commands,data, and programs into the implantable pulse generator 18 and retrievesdata out of the implantable pulse generator 18. In some configurations,the clinician programmer may communicate with more than one implantablepulse generator implanted in the same user.

The clinician programmer 36 may incorporate a custom programmed generalpurpose digital device, e.g., a custom program, industry standardhandheld computing platform or other personal digital assistant (PDA).The clinician programmer 36 can include an on-board microcontrollerpowered by a rechargeable battery. The rechargeable battery of theclinician programmer 36 may be recharged by being docked on a chargingbase (not shown); or the custom electronics of the clinician programmermay receive power from the connected PDA. The microcontroller carriesembedded code which may include pre-programmed rules or algorithms thatallow a clinician to remotely download program stimulus parameters andstimulus sequences parameters into the implantable pulse generator 18.The microcontroller of the clinician programmer 36 is also desirablyable to interrogate the implantable pulse generator and upload usagedata from the implantable pulse generator. FIG. 12 shows one possibleapplication where the clinician is using the programmer 36 tointerrogate the implantable pulse generator. FIG. 13 shows analternative application where the clinician programmer, or a clinicianprogrammer derivative 33 intended for remote programming applicationsand having the same or similar functionality as the clinicianprogrammer, is used to interrogate the implantable pulse generator. Ascan be seen, the clinician programmer derivative 33 is connected to alocal computer, allowing for remote interrogation via a local areanetwork, wide area network, or Internet connection, for example.

Using subsets of the clinician programmer software, features of theclinician programmer 36 or clinician programmer derivative 33 mightinclude the ability of the clinician or physician to remotely monitorand adjust parameters using the Internet or other known or futuredeveloped networking schemes. A clinician programmer derivative 33 woulddesirably connect to the patient's computer in their home through anindustry standard network such as the Universal Serial Bus (USB), wherein turn an applet downloaded from the clinician's server would containthe necessary code to establish a reliable transport level connectionbetween the implantable pulse generator 18 and the clinician's clientsoftware, using the clinician programmer derivative 33 as a bridge. Sucha connection may also be established through separately installedsoftware. The clinician or physician could then view relevant diagnosticinformation, such as the health of the unit or its current settings, andthen modify the stimulus settings in the IPG or direct the patient totake the appropriate action. Such a feature would save the clinician,the patient and the health care system substantial time and money byreducing the number of office visits during the life of the implant.

Other features of the clinician programmer, based on an industrystandard platform, might include the ability to connect to theclinician's computer system in his or hers office. Such features maytake advantage of the Conduit connection employed by Palm OS baseddevices. Such a connection then would transfer relevant patient data tothe host computer or server for electronic processing and archiving.With a feature as described here, the clinician programmer then becomesan integral link in an electronic chain that provides better patientservice by reducing the amount of paperwork that the physician's officeneeds to process on each office visit. It also improves the reliabilityof the service since it reduces the chance of mis-entered or mis-placedinformation, such as the record of the parameter setting adjusted duringthe visit.

With the use of a patient controller 37 (see FIG. 14), the wireless link38 allows a patient to control certain parameters of the implantablepulse generator within a predefined limited range. The parameters mayinclude the operating modes/states, increasing/decreasing or optimizingstimulus patterns, or providing open or closed loop feedback from anexternal sensor or control source. The wireless telemetry 38 alsodesirably allows the user to interrogate the implantable pulse generator18 as to the status of its internal battery 22. The full ranges withinthese parameters may be controlled, adjusted, and limited by aclinician, so the user may not be allowed the full range of possibleadjustments.

In one embodiment, the patient controller 37 is sized and configured tocouple to a key chain, as seen in FIG. 14. It is to be appreciated thatthe patient controller 37 may take on any convenient shape, such as aring on a finger, or a watch on a wrist, or an attachment to a belt, forexample. The patient controller may also use a magnetic switch to enablethe user to turn the IPG on/off.

The wireless telemetry may incorporate a suitable, low power wirelesstelemetry transceiver (radio) chip set that can operate in the MICS(Medical Implant Communications Service) band (402 MHz to 405 MHz) orother VHF/UHF low power, unlicensed bands. A wireless telemetry link notonly makes the task of communicating with the implantable pulsegenerator 18 easier, but it also makes the link suitable for use inmotor control applications where the user issues a command to theimplantable pulse generator to produce muscle contractions to achieve afunctional goal (e.g., to stimulate ankle flexion to aid in the gait ofan individual after a stroke) without requiring a coil or othercomponent taped or placed on the skin over the implanted implantablepulse generator.

Appropriate use of power management techniques is important to theeffective use of wireless telemetry. Desirably, the implantable pulsegenerator is exclusively the communications slave, with allcommunications initiated by the external controller (the communicationsmaster). The receiver chip of the implantable pulse generator is OFFmore than 99% of the time and is pulsed on periodically to search for acommand from an external controller, including but not limited to theclinician programmer 36 and the patient controller 37. Communicationsprotocols include appropriate check and message acknowledgmenthandshaking to assure the necessary accuracy and completeness of everymessage. Some operations (such as reprogramming or changing stimulusparameters) require rigorous message accuracy testing andacknowledgement. Other operations, such as a single user command valuein a string of many consecutive values, might require less rigorouschecking and a more loosely coupled acknowledgement.

The timing with which the implantable pulse generator enables itstransceiver to search for RF telemetry from an external controller isprecisely controlled (using a time base established by a quartz crystal)at a relatively low rate, e.g., the implantable pulse generator may lookfor commands from the external controller at a rate of less than one (1)Hz. This equates to a monitoring interval of several seconds. It is tobe appreciated that the monitoring rate may vary faster or slowerdepending on the application, (e.g., twice per second; i.e., every 500milliseconds). This allows the external controller to time when theimplantable pulse generator responds to a command and then tosynchronize its commands with when the implantable pulse generator willbe listening for commands. This, in turn, allows commands issued withina short time (seconds to minutes) of the last command to be captured andacted upon without having to ‘broadcast’ an idle or pause signal for 500milliseconds before actually issuing the command in order to know thatthe implantable pulse generator will have enabled its receiver andreceived the command. Similarly, the communications sequence isconfigured to have the external controller issue commands insynchronization with when the implantable pulse generator will belistening for a command. Similarly, the command set implemented isselected to minimize the number of messages necessary and the length ofeach message consistent with the appropriate level of error detectionand message integrity monitoring. It is to be appreciated that themonitoring rate may vary faster or slower depending on the application;and may vary over time within a given application.

A suitable radio chip is used for the half duplex wirelesscommunications, e.g., the AMIS-52100 (AMI Semiconductor; Pocatello,Id.). This transceiver chip is designed specifically for the MICS andits European counter-part the ULP-AMI (Ultra Low Power-Active MedicalImplant) band. This chip set is optimized by micro-power operation withrapid start-up, and RF ‘sniffing’ circuitry.

d. Stimulus Output Stage

According to one desirable technical feature, the implantable pulsegenerator 18 desirably uses a single stimulus output stage (generator)that is directed to one or more output channels (electrode surfaces) byanalog switch(es) or analog multiplexer(s). Desirably, the implantablepulse generator 18 will deliver at least one channel of stimulation viaa lead/electrode. For applications requiring more stimulus channels,several channels (perhaps up to four) can be generated by a singleoutput stage. In turn, two or more output stages could be used, eachwith separate multiplexing to multiple channels, to allow an implantablepulse generator with eight or more stimulus channels. The stimulationwaveform output of the IPG desirably has an asymmetrically biphasicwaveform (net DC current less than 10 μA), and an RC recovery phase withprogrammable interphase delay. The stimulus parameters (amplitude, pulseduration, and frequency) are independently adjustable with amplitudeoutput ranging from 0.5 mA to 20 mA, pulse duration ranging from 0 to500 microseconds, and frequency ranging from 1 (one) to 300 Hz. In oneembodiment, the applied stimulus frequency may be in the range of aboutone Hz to about fifteen Hz. The stimulus current (amplitude) and pulseduration being programmable on a channel to channel basis and adjustableover time based on a clinically programmed sequence or regime or basedon user (patient) commands received via the wireless communicationslink.

A circuit diagram showing a desired configuration for the stimulusoutput stage feature is shown in FIG. 17. It is to be appreciated thatmodifications to this circuit diagram configuration which produce thesame or similar functions as described are within the scope of theinvention.

Desirably, the implantable pulse generator 18 includes a single stimulusgenerator (with its associated DC current blocking output capacitor)which is multiplexed to a number of output channels; or a small numberof such stimulus generators each being multiplexed to a number of outputchannels. This circuit architecture allows multiple output channels withvery little additional circuitry. A typical, biphasic stimulus pulse isshown in FIG. 18. Note that the stimulus output stage circuitry 46 mayincorporate a mechanism to limit the recovery phase current to a smallvalue (perhaps 0.5 mA). Also note that the stimulus generator (and theassociated timing of control signals generated by the microcontroller)may provide a delay (typically of the order of 100 microseconds) betweenthe cathodic phase and the recovery phase to limit the recovery phasediminution of the cathodic phase effective at eliciting a neuralexcitation. The charge recovery phase for any electrode (cathode) mustbe long enough to assure that all of the charge delivered in thecathodic phase has been returned in the recovery phase; i.e., greaterthan or equal to five time constants are allowed for the recovery phase.This will allow the stimulus stage to be used for the next electrodewhile assuring there is no net DC current transfer to any electrode.Thus, the single stimulus generator having this characteristic would belimited to four channels (electrodes), each with a maximum frequency of30 Hz to 50 Hz. This operating frequency exceeds the needs of manyindications for which the implantable pulse generator is well suited.For applications requiring more channels (or higher composite operatingfrequencies), two or more separate output stages might each bemultiplexed to multiple (e.g., four) electrodes.

e. The Lead Connection Header

According to one desirable technical feature, the implantable pulsegenerator 18 desirably includes a lead connection header 14 forconnecting the lead(s) 12 that will enable reliable and easy replacementof the lead/electrode (see FIGS. 7A and 7B), and includes a smallantenna 54 for use with the wireless telemetry feature.

The implantable pulse generator desirably incorporates a connectionheader (top header) 14 that is easy to use, reliable, and robust enoughto allow multiple replacements of the implantable pulse generator aftermany years (e.g., more than ten years) of use. The surgical complexityof replacing an implantable pulse generator is usually low compared tothe surgical complexity of correctly placing the implantable lead12/electrode 16 in proximity to the target nerve/tissue and routing thelead 12 to the implantable pulse generator. Accordingly, the lead 12 andelectrode 16 desirably has a service life of at least ten years with aprobable service life of fifteen years or more. Based on the clinicalapplication, the implantable pulse generator may not have this long aservice life. The implantable pulse generator service life is largelydetermined by the power capacity of the Lithium Ion battery 22, and islikely to be three to ten years, based on the usage of the device.Desirably, the implantable pulse generator 18 has a service life of atleast three years.

As described above, the implantable pulse generator preferably will usea laser welded titanium case. As with other active implantable medicaldevices using this construction, the implantable lead(s) 12 connect tothe implantable pulse generator through a molded or cast polymericconnection header 14 (top header). Metal-ceramic or metal-glassfeed-thrus maintain the hermetic seal of the titanium capsule whileproviding electrical contact to the electrical contacts of the lead12/electrode 16.

The standard implantable connectors may be similar in design andconstruction to the low-profile IS-1 connector system (per ISO 5841-3).The IS-1 connectors have been in use since the late 1980s and have beenshown to be reliable and provide easy release and re-connection overseveral implantable pulse generator replacements during the service lifeof a single pacing lead. Full compatibility with the IS-1 standard, andmating with pacemaker leads, is not a requirement for the implantablepulse generator.

The implantable pulse generator connection system may include amodification of the IS-1 connector system, which shrinks the axiallength dimensions while keeping the format and radial dimensions of theIS-1. For application with more than two electrode conductors, the topheader 14 may incorporate one or more connection receptacles each ofwhich accommodate leads with typically four conductors. When two or moreleads are accommodated by the header, these leads may exit theconnection header in opposite directions (i.e., from opposite sides ofthe header).

These connectors can be similar to the banded axial connectors used byother multi-polar implantable pulse generators or may follow theguidance of the draft IS-4 implantable connector standard. The design ofthe implantable pulse generator housing and header 14 preferablyincludes provisions for adding the additional feed-thrus and largerheaders for such indications.

The inclusion of the UHF antenna 54 for the wireless telemetry insidethe connection header (top header) 14 is necessary as the shieldingoffered by the titanium case will severely limit (effectively eliminate)radio wave propagation through the case. The antenna 54 connection willbe made through a feed-thru similar to that used for the electrodeconnections. Alternatively, the wireless telemetry signal may be coupledinside the implantable pulse generator onto a stimulus output channeland coupled to the antenna 54 with passive filtering/couplingelements/methods in the connection header 14.

f. The Microcontroller

According to one desirable technical feature, the implantable pulsegenerator 18 desirably uses a standard, commercially availablemicro-power, flash programmable microcontroller 24 or processor core inan application specific integrated circuit (ASIC). This device (orpossibly more than one such device for a computationally complexapplication with sensor input processing) and other large semiconductorcomponents may have custom packaging such as chip-on-board, solder flipchip, or adhesive flip chip to reduce circuit board real estate needs.

A circuit diagram showing a desired configuration for themicrocontroller 24 is shown in FIG. 19. It is to be appreciated thatmodifications to this circuit diagram configuration which produce thesame or similar functions as described are within the scope of theinvention.

g. Power Management Circuitry

According to one desirable technical feature, the implantable pulsegenerator 18 desirably includes efficient power management circuitry asan element of the implantable pulse generator circuitry 20 shown in FIG.15. The power management circuitry is generally responsible for theefficient distribution of power and monitoring the battery 22. Inaddition, the operation of the implantable pulse generator 18 can bedescribed in terms of having operating modes as relating to the functionof the power management circuitry. These modes may include, but are notlimited to IPG Active and IPG Dormant. These modes will be describedbelow in terms of the principles of operation of the power managementcircuitry using possible circuit diagrams shown in FIGS. 20 and 21. FIG.20 shows one possible power management sub-circuit having MOSFETisolation between the battery 22 and a charger circuit (when used). FIG.21 shows another possible power management sub-circuit diagram withouthaving MOSFET isolation between the battery 22 and the charger circuit(when used). In the circuit without the isolation MOSFET (see FIG. 21),the leakage current of the disabled charge control integrated circuitchip (U1) must be very low to prevent this leakage current fromdischarging the battery 22 in all modes (including the Dormant Mode).Except as noted, the description of these modes applies to bothcircuits.

i. IPG Active Mode

The IPG Active mode occurs when the implantable pulse generator 18 isoperating normally. In this mode, the implantable pulse generator may begenerating stimulus outputs or it may be waiting for the next request togenerate stimulus in response to a timed neuromodulation sequence or atelemetry command from an external controller. In this mode, theimplantable pulse generator is active (microcontroller 24 is powered andcoordinating wireless communications and may be timing & controlling thegeneration and delivery of stimulus pulses).

i (a). Principles of Operation, IPG Active Mode

In the IPG Active mode, as can be seen in FIG. 20, the lack of DCcurrent from VRAW means that Q5 is held off. This, in turn, holds Q3 offand a portion of the power management circuitry is isolated from thebattery 22. In FIG. 21, the lack of DC current from VRAW means that U1is disabled. This, in turn, keeps the current drain from the battery 22to an acceptably low level, typically less than 1 μA.

ii. IPG Dormant Mode

The IPG Dormant mode occurs when the implantable pulse generator 18 iscompletely disabled (powered down). In this mode, power is not beingsupplied to the microcontroller 24 or other enabled circuitry. This isthe mode for the long-term storage of the implantable pulse generatorbefore or after implantation. The Dormant mode may only be exited byplacing a pacemaker magnet (or comparable device) over the implantablepulse generator 18 for a predetermined amount of time, e.g., fiveseconds.

ii (a). Principles of Operation, IPG Dormant Mode

In the IPG Dormant mode, VBAT is not delivered to the remainder of theimplantable pulse generator circuitry because Q4 is turned off. TheDormant mode is stable because the lack of VBAT means that VCC is alsonot present, and thus Q6 is not held on through R8 and R10. Thus thebattery 22 is completely isolated from all load circuitry (the VCC powersupply and the VHH power supply).

The Dormant mode is entered through the application of a long magnetplacement over S1 (magnetic reed switch) or through the reception of acommand by the wireless telemetry. In the case of the telemetry command,the PortD4, which is normally configured as a microcontroller input, isconfigured as a logic output with a logic low (0) value. This, in turn,discharges C8 through R12 and turns off Q6; which, in turn, turns off Q4and forces the implantable pulse generator into the Dormant mode. Notethat R12 is much smaller in value than R10, thus the microcontroller 24can force C8 to discharge even though VCC is still present.

In FIG. 20, the lack of DC current from VRAW means that Q5 is held off.This, in turn, holds Q3 off and a portion of the power managementcircuitry is isolated from the battery 22. Also, Q4 was turned off. InFIG. 21, the lack of DC current from VRAW means that U1 is disabled.This, in turn, keeps the current drain from the battery 22 to anacceptably low level, typically less than 1 μA.

2. Representative Implantable Pulse Generator Circuitry

FIG. 15 shows an embodiment of a block diagram circuit 20 for theprimary cell implantable pulse generator 18 that takes into account thedesirable technical features discussed above. The circuit 20 can begrouped into functional blocks, which generally correspond to theassociation and interconnection of the electronic components.

In FIG. 15, seven functional blocks are shown: (1) The Microprocessor orMicrocontroller 24; (2) the Power Management Circuit 40; (3) the VCCPower Supply 42; (4) the VHH Power Supply 44; (5) the Stimulus OutputStage(s) 46; (6) the Output Multiplexer(s) 48; and (7) the WirelessTelemetry Circuit 50.

For each of these blocks, the associated functions, possible keycomponents, and circuit description are now described.

a. The Microcontroller

The Microcontroller 24 is responsible for the following functions:

(1) The timing and sequencing of the stimulator stage and the VHH powersupply used by the stimulator stage,

(2) The sequencing and timing of power management functions,

(3) The monitoring of the battery voltage, the stimulator voltagesproduced during the generation of stimulus pulses, and the total circuitcurrent consumption, VHH, and VCC,

(4) The timing, control, and interpretation of commands to and from thewireless telemetry circuit,

(5) The logging (recording) of patient usage data as well as clinicianprogrammed stimulus parameters and configuration data, and

(6) The processing of commands (data) received from the user (patient)via the wireless link to modify the characteristics of the stimulusbeing delivered.

The use of a microcontroller incorporating flash programmable memoryallows the operating program of the implantable pulse generator as wellas the stimulus parameters and settings to be stored in non-volatilememory (data remains safely stored even if the battery 22 becomes fullydischarged; or if the implantable pulse generator is placed in theDormant mode). Yet, the data (operating program, stimulus parameters,usage history log, etc.) can be erased and reprogrammed thousands oftimes during the life of the implantable pulse generator. The software(firmware) of the implantable pulse generator must be segmented tosupport the operation of the wireless telemetry routines while the flashmemory of the microcontroller 24 is being erased and reprogrammed.Similarly, the VCC power supply 42 must support the power requirementsof the microcontroller 24 during the flash memory erase and programoperations.

Although the microcontroller 24 may be a single component, the firmwareis developed as a number of separate modules that deal with specificneeds and hardware peripherals. The functions and routines of thesesoftware modules are executed sequentially; but the execution of thesemodules are timed and coordinated so as to effectively functionsimultaneously. The microcontroller operations that are associateddirectly with a given hardware functional block are described with thatblock.

The Components of the Microcontroller Circuit may include:

(1) A single chip microcontroller 24. This component may be a member ofthe Texas Instruments MSP430 family of flash programmable, micro-power,highly integrated mixed signal microcontroller. Likely family members tobe used include the MSP430F1610, MSP430F1611, MSP430F1612, MSP430F168,and the MSP430F169. Each of these parts has numerous internalperipherals, and a micropower internal organization that allows unusedperipherals to be configured by minimal power dissipation, and aninstruction set that supports bursts of operation separated by intervalsof sleep where the microcontroller suspends most functions.

(2) A miniature, quartz crystal (X1) for establishing precise timing ofthe microcontroller. This may be a 32.768 KHz quartz crystal.

(3) Miscellaneous power decoupling and analog signal filteringcapacitors.

b. Power Management Circuit

The Power Management Circuit 40 (including associated microcontrolleractions) is responsible for the following functions:

(1) monitor the battery voltage,

(2) suspend stimulation when the battery voltage becomes very low,and/or suspend all operation (go into the Dormant mode) when the batteryvoltage becomes critically low,

(3) communicate (through the wireless telemetry link 38) with theexternal equipment the charge status of the battery 22,

(4) prevent (with single fault tolerance) the delivery of excessivecurrent from the battery 22, (5) provide battery power to the rest ofthe circuitry of the implantable pulse generator, i.e., VCC and VHHpower supplies,

(6) provide isolation of the Lithium Ion battery 22 from other circuitrywhile in the Dormant mode,

(7) provide a hard microprocessor reset and force entry into the Dormantmode in the presence of a pacemaker magnet (or comparable device), and

(8) provide the microcontroller 24 with analog voltages with which tomeasure the magnitude of the battery voltage and the appropriate batterycurrent flow (drain and charge).

The Components of the Power Management Circuit may include:

(1) Low on resistance, low threshold P channel MOSFETs with very low offstate leakage current (Q2, Q3, Q4).

(2) Analog switches (or an analog multiplexer) U3.

(3) Logic translation N-channel MOSFETs (Q5 & Q6) with very low offstate leakage current.

c. The VCC Power Supply

The VCC Power Supply 42 is generally responsible for the followingfunctions:

(1) Some of the time, the VCC power supply passes the battery voltage tothe circuitry powered by VCC, such as the microcontroller 24, stimulatoroutput stage 46, wireless telemetry circuitry 50, etc.

(2) At other times, the VCC power supply fractionally steps up thevoltage to about 3.3V; (other useable voltages include 3.0V, 2.7V, etc.)despite changes in the Lithium Ion battery 22 voltage. This highervoltage is required for some operations such as programming or erasingthe flash memory in the microcontroller 24, (i.e., in circuitprogramming).

The voltage converter/switch part at the center of the VCC power supplymay be a charge pump DC to DC converter. Typical choices for this partmay include the Maxim MAX1759, the Texas Instruments TPS60204, or theTexas Instruments REG710, among others.

The characteristics of the VCC Power Supply might include:

(1) high efficiency and low quiescent current, i.e., the current wastedby the power supply in its normal operation. This value should be lessthan a few microamperes; and

(2) drop-out voltage, i.e., the minimal difference between the VBATsupplied to the VCC power supply and its output voltage. This voltagemay be less than about 100 mV even at the current loads presented by thetransmitter of the wireless telemetry circuitry 50.

(3) The VCC power supply 42 may allows in-circuit reprogramming of theimplantable pulse generator firmware, or optionally, the implantablepulse generator 18 may not use a VCC power supply, which may not allowin-circuit reprogramming of the implantable pulse generator firmware.

d. VHH Power Supply

A circuit diagram showing a desired configuration for the VHH powersupply 44 is shown in FIG. 22. It is to be appreciated thatmodifications to this circuit diagram configuration which produce thesame or similar functions as described are within the scope of theinvention.

The VHH Power Supply 44 is generally responsible for the followingfunctions:

(1) Provide the Stimulus Output Stage 46 and the Output Multiplexer 48with a programmable DC voltage between the battery voltage and a voltagehigh enough to drive the required cathodic phase current through theelectrode circuit plus the voltage drops across the stimulator stage,the output multiplexer stage, and the output coupling capacitor. VHH istypically 12 VDC or less for neuromodulation applications; and 25V orless for muscle stimulation applications.

The Components of the VHH Power Supply might include:

(1) Micropower, inductor based (fly-back topology) switch mode powersupply (U10); e.g., Texas Instruments TPS61045, Texas InstrumentsTPS61041, or Linear Technology LT3464 with external voltage adjustmentcomponents.

(2) L6 is the flyback energy storage inductor.

(3) C42 & C43 form the output capacitor.

(4) R27, R28, and R29 establish the operating voltage range for VHHgiven the internal DAC which is programmed via the SETVHH logic commandfrom the microcontroller 24.

(5) Diode D9 serves no purpose in normal operation and is added to offerprotection from over-voltage in the event of a VHH circuit failure.

(6) The microcontroller 24 monitors VHH for detection of a VHH powersupply failure, system failures, and optimizing VHH for the exhibitedelectrode circuit impedance.

e. Stimulus Output Stage

The Stimulus Output Stage(s) 46 is responsible for the followingfunctions:

(1) Generate the identified biphasic stimulus current with programmable(dynamically adjustable during use) cathodic phase amplitude, pulsewidth, and frequency. The recovery phase may incorporate a maximumcurrent limit; and there may be a delay time (most likely a fixed delay)between the cathodic phase and the recovery phase (see FIG. 18). Typicalcurrents (cathodic phase) for neuromodulation applications range betweenabout 100 microamps and about 20 milliamps. For applications using nervecuff electrodes or other electrodes that are in very close proximity tothe excitable neural tissue, stimulus amplitudes of less than onemilliamp might be necessary because of this close proximity. Electrodecircuit impedances can vary with the electrode and the application, butare likely to be less than 2,000 ohms and greater than 100 ohms across arange of electrode types.

The Components of the Stimulus Output Stage may include:

(1) The cathodic phase current through the electrode circuit isestablished by a high gain (HFE) NPN transistor (Q7) with emitterdegeneration. In this configuration, the collector current of thetransistor (Q7) is defined by the base drive voltage and the value ofthe emitter resistor (R24).

Two separate configurations are possible: In the first configuration (asshown in FIG. 17), the base drive voltage is provided by a DACperipheral inside the microcontroller 24 and is switched on and off by atimer peripheral inside the microcontroller. This switching function isperformed by an analog switch (U8). In this configuration, the emitterresistor (R24) is fixed in value and fixed to ground.

In a second alternative configuration, the base drive voltage is a fixedvoltage pulse (e.g., a logic level pulse) and the emitter resistor ismanipulated under microcontroller control. Typical options may includeresistor(s) terminated by microcontroller IO port pins that are held orpulsed low, high, or floating; or an external MOSFET that pulls one ormore resistors from the emitter to ground under program control. Notethat the pulse timing need only be applied to the base drive logic; thetiming of the emitter resistor manipulation is not critical.

The transistor (Q7) desirably is suitable for operation with VHH on thecollector. The cathodic phase current through the electrode circuit isestablished by the voltage drop across the emitter resistor. Diode D7,if used, provides a degree of temperature compensation to this circuit.

(2) The microcontroller 24 (preferably including a programmablecounter/timer peripheral) generates stimulus pulse timing to generatethe cathodic and recovery phases and the interphase delay. Themicrocontroller 24 also monitors the cathode voltage to confirm thecorrect operation of the output coupling capacitor, to detect systemfailures, and to optimize VHH for the exhibited electrode circuitimpedance; i.e., to measure the electrode circuit impedance.Additionally, the microcontroller 24 can also monitor the pulsingvoltage on the emitter resistor; this allows the fine adjustment of lowstimulus currents (cathodic phase amplitude) through changes to the DACvalue.

f. The Output Multiplexer

The Output Multiplexer 48 is responsible for the following functions:

(1) Route the Anode and Cathode connections of the Stimulus Output Stage46 to the appropriate electrode based on addressing data provided by themicrocontroller 24.

(2) Allow recharge (recovery phase) current to flow from the outputcoupling capacitor back through the electrode circuit with aprogrammable delay between the end of the cathodic phase and thebeginning of the recovery phase (the interphase delay).

The circuit shown in FIG. 17 may be configured to provide monopolarstimulation (using the case 26 as the return electrode) to Electrode 1,to Electrode 2, or to both through time multiplexing. This circuit couldalso be configured as a single bipolar output channel by changing thehardwire connection between the circuit board and the electrode; i.e.,by routing the CASE connection to Electrode 1 or Electrode 2. The use offour or more channels per multiplexer stage (i.e., per output couplingcapacitor) is possible.

The Components of the Output Multiplexer might include:

(1) An output coupling capacitor in series with the electrode circuit.This capacitor is desirably located such that there is no DC across thecapacitor in steady state. This capacitor is typically charged by thecurrent flow during the cathodic phase to a voltage range of about ¼thto 1/10th of the voltage across the electrode circuit during thecathodic phase. Similarly, this capacitor is desirably located in thecircuit such that the analog switches do not experience voltages beyondtheir ground of power supply (VHH).

(2) The analog switches (U7) must have a suitably high operatingvoltage, low ON resistance, and very low quiescent current consumptionwhile being driven from the specified logic levels. Suitable analogswitches include the Vishay/Siliconix DG412HS, for example.

(3) Microcontroller 24 selects the electrode connections to carry thestimulus current (and time the interphase delay) via address lines.

(4) Other analog switches (U9) may be used to sample the voltage of VHH,the CASE, and the selected Electrode. The switched voltage, after thevoltage divider formed by R25 and R26, is monitored by themicrocontroller 24.

g. Wireless Telemetry Circuit

The Wireless Telemetry circuit 50 is responsible for the followingfunctions:

(1) Provide reliable, bidirectional communications (half duplex) with anexternal controller, programmer, or an optional charger 34, for example,via a VHF-UHF RF link (likely in the 402 MHZ to 405 MHz MICS band perFCC 47 CFR Part 95 and the Ultra Low Power-Active Medical Implant (AMI)regulations of the European Union). This circuit will look for RFcommands at precisely timed intervals (e.g., twice a second), and thisfunction must consume very little power. Much less frequently thiscircuit will transmit to the external controller. This function shouldalso be as low power as possible; but will represent a lower totalenergy demand than the receiver in most of the anticipated applications.The RF carrier is amplitude modulated (on-off keyed) with the digitaldata. Serial data is generated by the microcontroller 24 alreadyformatted and timed. The wireless telemetry circuit 50 converts theserial data stream into a pulsing carrier signal during the transitprocess; and it converts a varying RF signal strength into a serial datastream during the receive process.

The Components of the Wireless Telemetry Circuit might include:

(1) a crystal controlled, micropower transceiver chip such as the AMISemiconductor AMIS-52100 (U6). This chip is responsible for generatingthe RF carrier during transmissions and for amplifying, receiving, anddetecting (converting to a logic level) the received RF signals. Thetransceiver chip must also be capable of quickly starting and stoppingoperation to minimize power consumption by keeping the chip disabled(and consuming very little power) the majority of the time; and poweringup for only as long as required for the transmitting or receivingpurpose.

(2) The transceiver chip has separate transmit and receive ports thatmust be switched to a single antenna/feedthru. This function isperformed by the transmit/receive switch (U5) under microcontrollercontrol via the logic line XMIT. The microcontroller 24 controls theoperation of the transceiver chip via an I²C serial communications link.The serial data to and from the transceiver chip may be handled by aUART or a SPI peripheral of the microcontroller. The messageencoding/decoding and error detection may be performed by a separate,dedicated microcontroller; else this processing will be time shared withthe other tasks of the only microcontroller.

The various inductor and capacitor components (U6) surrounding thetransceiver chip and the transmit/receive switch (U5) are impedancematching components and harmonic filtering components, except asfollows:

(1) X2, C33 and C34 are used to generate the crystal controlled carrier,desirably tuned to the carrier frequency divided by thirty-two,

(2) L4 and C27 form the tuned elements of a VCO (voltage controlledoscillator) operating at twice the carrier frequency, and

(3) R20, C29, and C30 are filter components of the PLL (phase lockedloop) filter.

B. Lead and Electrode

As previously described, the system 10 includes an implantable pulsegenerator 18, a lead 12, and an electrode 16. Two possible types ofelectrodes will be described below, although any number of electrodetypes may be used.

1. Implantation in Adipose Tissue

Neurostimulation leads and electrodes that may be well suited forimplantation in muscle tissue are not well suited for implantation insoft adipose tissue in the targeted location at or near the pubicsymphysis. This is because adipose tissue is unlike muscle tissue, andalso because the vascularization and innervation of tissue at or nearthe pubic symphysis is unlike tissue in a muscle mass. Muscular tissueis formed by tough bundles of fibers with intermediate areolar tissue.The fibers consist of a contractile substance enclosed in a tubularsheath. The fibers lend bulk, density, and strength to muscle tissuesthat are not found in soft adipose tissue. Muscles are also notinnervated with sensory nerves or highly vascularized with blood vesselsto the extent found in the pubic region of the body.

Adipose tissue (see FIG. 23) consists of small vesicles, calledfat-cells, lodged in the meshes of highly vascularized areolar tissuecontaining minute veins, minute arteries, and capillary blood vessels.The fat-cells vary in size, but are about the average diameter of 1/500of an inch. They are formed of an exceedingly delicate protoplasmicmembrane, filled with fatty matter, which is liquid during life andturns solid after death. They are round or spherical where they have notbeen subject to pressure; otherwise they assume a more or less angularoutline. The fat-cells are contained in clusters in the areolae of fineconnective tissue, and are held together mainly by a network ofcapillary blood vessels, which are distributed to them.

In one embodiment, the lead 12 and electrode 16 are sized and configuredto be inserted into and to rest in soft adipose tissue (see FIG. 23),such as in the lower abdomen for example, without causing pain ordiscomfort or impact body image. Desirably, the lead 12 and electrode 16can be inserted using a small (e.g., smaller than 16 gauge) introducerwith minimal tissue trauma. The lead 12 and electrode 16 are formed froma biocompatible and electrochemically suitable material and possess nosharp features that can irritate tissue during extended use.Furthermore, the lead 12 and electrode 16 possess mechanicalcharacteristics including mechanical compliance (flexibility) alongtheir axis (axially), as well as perpendicular to their axis (radially),and unable to transmit torque, to flexibly respond to dynamicstretching, bending, and crushing forces that can be encountered withinsoft, mobile adipose tissue in this body region without damage orbreakage, and to accommodate relative movement of the pulse generator 18coupled to the lead 12 without imposing force or torque to the electrode16 which tends to dislodge the electrode.

Furthermore, the lead 12 and electrode 16 desirably include an anchoringmeans 70 for providing retention strength to resist migration within orextrusion from soft, mobile adipose tissue in this body region inresponse to force conditions normally encountered during periods ofextended use (see FIG. 24). In addition, the anchoring means 70 isdesirably sized and configured to permit the electrode 16 position to beadjusted easily during insertion, allowing placement at the optimallocation where bilateral stimulation of the left and right branches ofthe genital nerves occurs. The anchoring means 70 functions to hold theelectrode at the implanted location despite the motion of the tissue andsmall forces transmitted by the lead due to relative motion of theconnected pulse generator due to changes in body posture or externalforces applied to the abdomen. However, the anchoring means 70 shouldallow reliable release of the electrode 16 at higher force levels, topermit withdrawal of the implanted electrode 16 by purposeful pulling onthe lead 12 at such higher force levels, without breaking or leavingfragments, should removal of the implanted electrode 16 be desired.

The lead 12 and electrode 16 is sized and configured to be anchoredsolely in soft adipose tissue, with no dependence on support orstability from muscle tissue. The lead 12 and electrode 16 areparticularly well suited for placement in this soft adipose tissuebecause of the unique shape, size, spacing, and orientation of theanchoring means 70, which allows the lead 12 and electrode 16 to be usedfor other indications in addition to sexual restoration, such as in thefield of urology (e.g., stimulation of nerves in adipose tissue for thetreatment of incontinence).

a. The Lead

FIGS. 26 and 27 show a representative embodiment of a lead 12 andelectrode 16 that provide the foregoing features. The implantable lead12 comprises a molded or extruded component 72, which encapsulates acoiled stranded wire element 74, and a connector 75 (shown in FIG. 24).The wire element may be trifilar, as shown in FIG. 26, and may beconstructed of coiled MP35N nickel-cobalt wire or wires that have beencoated in polyurethane. The molded or extruded lead 12 can have anoutside diameter as small as about one (1) mm. The lead 12 may beapproximately 10 cm to 40 cm in length. The lead 12 provides electricalcontinuity between the connector 75 and the electrode 16.

The coil's pitch can be constant or, as FIG. 26 shows, the coil's pitchcan alternate from high to low spacing to allow for flexibility in bothcompression and tension. The tight pitch will allow for movement intension, while the open pitch will allow for movement in compression.

A standard IS-1 or similar type connector 75 at the proximal endprovides electrical continuity and mechanical attachment to the IPG. Thelead 12 and connector 75 all may include provisions for a guidewire thatpasses through these components and the length of the lead 12 to theconductive electrode 16 at the distal end.

b. The Electrode

The electrode 16 may comprise one or more electrically conductivesurfaces. Two conductive surfaces are show in FIG. 24. The twoconductive surfaces can be used either A) as two individual stimulating(cathodic) electrodes in monopolar configuration using the casing 26 ofthe IPG 18 as the return (anodic) electrode or B) in bipolarconfiguration with one electrode functioning as the stimulating(cathodic) electrode and the other as the return (anodic) electrode.

In general, bipolar stimulation is more specific than monopolarstimulation—the area of stimulation is much smaller—which is good if theelectrode 16 is close to the target nerve N. But if the electrode 16 isfarther from the target nerve N, then a monopolar configuration could beused because with the IPG 18 acting as the return electrode, activationof the nerve is less sensitive to exact placement than with a bipolarconfiguration.

In use, a physician may first attempt to place the electrode 16 close tothe target nerve N so that it could be used in a bipolar configuration,but if bipolar stimulation failed to activate the nerve, then theelectrode 16 could be switched to a monopolar configuration. Twoseparate conductive surfaces on the electrode 16 provide an advantagebecause if one conductive surface fails to activate the target nerve Nbecause it is too far from the nerve, then stimulation with the secondconductive surface could be tried, which might be closer to the targetnerve N. Without the second conductive surface, a physician would haveto reposition the electrode to try to get closer to the target nerve N.

The electrode 16, or electrically conductive surface or surfaces, can beformed from PtIr (platinum-iridium) or, alternatively, 316L stainlesssteel, and possess a conductive surface of approximately 10 mm²-20 mm².This surface area provides current densities up to 2 mA/mm2 with perpulse charge densities less than 0.5 μC/mm2. These dimensions andmaterials deliver a charge safely within the stimulation levels suppliedby the IPG.

Each conductive surface has an axial length in the range of about threeto five millimeters in length. When two or more conductive surfaces areused, either in the monopolar or bipolar configurations as described,there will be an axial spacing between the conductive surfaces in therange of 1.5 to 2.5 millimenters.

c. The Anchoring Means

In the illustrated embodiment (see FIGS. 24 and 25), the lead isanchored by anchoring means 70 specifically designed to secure theelectrode 16 in the layer of adipose tissue in electrical proximity tothe target nerve N, without the support of muscle tissue. The anchoringmeans 70 takes the form of an array of shovel-like blades or scallops 76proximal to the proximal-most electrode 16 (although a blade 76 orblades could also be proximal to the distal most electrode 16, or couldalso be distal to the distal most electrode 16). The blades 76 aredesirably present relatively large, generally planar surfaces, and areplaced in multiple rows axially along the lead 12. The blades 76 mayalso be somewhat arcuate as well, or a combination of arcuate and planarsurfaces. A row of blades 76 comprises two blades 76 spaced 180 degreesapart. The blades 76 may have an axial spacing between rows of blades inthe range of six to fourteen millimeters, and each row may be spacedapart 90 degrees. The blades 76 are normally biased toward a radiallyoutward condition into tissue. In this condition, the large surface areaand orientation of the blades 76 allow the lead 12 to resistdislodgement or migration of the electrode 16 out of the correctlocation in the surrounding tissue. In the illustrated embodiment, theblades 76 are biased toward a proximal-pointing orientation, to betterresist proximal migration of the electrode 16 with lead tension. Theblades 76 are desirably made from a polymer material, e.g., highdurometer silicone, polyurethane, or polypropylene, bonded to or moldedwith the lead 12.

The blades 76 can be deflected toward a distal direction in response toexerting a pulling force on the lead 12 at a threshold axial forcelevel, which is greater than expected day-to-day axial forces. Theblades 76 are sized and configured to yield during proximal passagethrough tissue in result to such forces, causing minimal tissue trauma,and without breaking or leaving fragments, despite the possible presenceof some degree of tissue in-growth. This feature permits the withdrawalof the implanted electrode 16, if desired, by purposeful pulling on thelead 12 at the higher axial force level.

Desirably, the anchoring means 70 is prevented from fully engaging bodytissue until after the electrode 16 has been deployed. The electrode 16is not deployed until after it has been correctly located during theimplantation (installation) process.

More particularly, and as will be described in greater detail later, thelead 12 and electrode 16 are intended to be percutaneously introducedthrough a sleeve 154 shown in FIG. 40 (this is also shown in FIGS. 41and 42). As shown in FIG. 28, the blades 76 assume a collapsed conditionagainst the lead 12 body when within the sleeve 154. In this condition,the blades 76 are shielded from contact with tissue. Once the locationis found, the sleeve 154 can be withdrawn, holding the lead 12 andelectrode 16 stationary. Free of the sleeve 154, the blades 76 springopen to assume their radially deployed condition in tissue, fixing theelectrode 16 in the desired location.

The position of the electrode 16 relative to the anchoring means 70, andthe use of the sleeve 154, allows for both advancement and retraction ofthe electrode delivery sleeve 154 during implantation whilesimultaneously delivering test stimulation. The sleeve 154 can be drawnback relative to the lead 12 to deploy the electrode 16 anchoring means70, but only when the physician determines that the desired electrodelocation has been reached. The withdrawal of the sleeve 154 from thelead 12 causes the anchoring means 70 to deploy without changing theposition of electrode 16 in the desired location (or allowing only asmall and predictable, set motion of the electrode). Once the sleeve 154is removed, the flexible, silicone-coated or polyurethane-coat lead 12and electrode 16 are left implanted in the tissue.

2. Molded Nerve Cuff

In an alternative embodiment, a lead 12 and a cuff electrode 16′ may beused. As FIG. 29 shows, the cuff electrode 16′ includes at least oneelectrically conductive surface 88. In the illustrated embodiment, thereare three individually controllable electrically conductive surfaces 88,although more or less may be used. The surface 88 may be solid, as shownin FIG. 31, or the surface may be segmented into isolated conductivesegments electrically coupled by a wire, as shown in FIG. 32. It is tobe appreciated that additional alternative configurations are possibleas well.

In this arrangement, the lead 12 (see FIG. 33) comprises a moldedcomponent 98, which encapsulates a coiled trifilar stranded wire element100. Each wire of the element 100 is coupled to one of the electricallyconductive solid or segmented surfaces 88. These surfaces may bemanufactured using a thin film of metal deposited on a liquid crystalpolymer substrate, or from strips of platinum, for example.

As FIG. 29 shows, the cuff electrode 16′ comprises a body 90 that may bemolded from a low durometer elastomer material 106 (e.g., silicone, suchas a two part, translucent, pourable silicone elastomer, e.g., NusilMED-4211). The electrically conductive surfaces 88 are integrated withthe body 90 during the molding process. Additional alternativeconfigurations of segmented conductive surfaces and the molding processof the cuff electrode 16′ is described in co-pending U.S. patentapplication Ser. No. 11/196,995, filed 4 Aug. 2005 and entitled“Devices, Systems, and Methods Employing a Molded Nerve Cuff Electrode,”which is incorporated herein by reference.

The molded body 90 of the cuff electrode 16′ is shaped or formed duringthe molding process to normally assume a curled or tubular spiral orrolled configuration. As shown in FIG. 29, in its normal coiledcondition, the body 90 extends in a spiral having a range of about 450degrees to about 560 degrees from end to end, and in one embodimentabout 540 degrees from end to end. The body 90 can be elasticallyuncoiled to increase its inner diameter (as FIGS. 33 and 34 show), e.g.,to be initially fitted about the periphery of the target nerve N, and inresponse to post-operative changes in the diameter of the target nerve Nthat might occur due to swelling. The elasticity of the body 90 wrapsthe electrically conductive surfaces snugly against the periphery of thetargeted nerve N. The elasticity of the body 90 is selected to snuglywrap about the target nerve N without causing damage or trauma. To thisend, it is believed desirable that the elastic memory of the cuffelectrode 16′ exhibits a predictable and repeatable pressure vs.diameter relationship that gradually increases pressure with increase indiameter to allow the electrode to fit snuggly about the periphery of anerve, but not too tightly to cause damage (i.e., exerts a maximumpressure about the target nerve N that does not exceed about 20 mmHg).

As FIG. 29 shows, the electrode 16′, being a molded component, desirablyincludes a molded or over-molded section forming a strain relief boot110 at the junction between the lead 12 and the cuff body 90. The boot110 strengthens the junction, to resist the effect of torque forces thatmight be applied during implantation and use along the lead 12. Inaddition, the strain relief boot 110 helps to prevent tension and/ormotion from damaging the lead to cuff interface for a longer flex life.FIG. 30 shows an alternative embodiment where the lead 12 and strainrelief boot 110 are generally parallel to the cuff body 90. The strainrelief boot 110 may take on any desired shape (i.e., coiled, bent, cone,or zigzag) to aid in its strain relief properties and to improvemanufacturability. It is to be appreciated that the lead to cuffinterface may be at any desired angle and is not limited to a parallelor perpendicular configuration.

As FIG. 34 shows, when wrapped about the target nerve N, theelectrically conductive surfaces 88 make and sustain circumferentialcontact substantially about the entire periphery of the target nerve N.In an alternative embodiment shown in FIGS. 35 and 36, the electricallyconductive surfaces 88 may be positioned so as to make contact with thetarget nerve N along the axis of the nerve, and around only a portion ofthe circumference of the target nerve N. FIG. 35 shows an uncoiled cuffbody 90 including three electrically conductive surfaces 88. FIG. 36shows the conductive surfaces 88 positioned along a length (the axis) ofthe target nerve N.

In a representative embodiment, the body 90 possesses a minimum diameter(when in its normally coiled condition) of as small as one (1) mm, whichmakes it well suited for implantation about small nerves. The minimumdiameter of the body 90 can, of course, be molded to possess largerminimum diameters, to provide a family of nerve cuff electrodes 16′ ofdifferent diameters that accommodate the range of diameters of human andanimal nerves, from small to large.

The electrically conductive surfaces 88 are made, e.g., from strips ofplatinum, either as one long strip, or as segmented strips that areconnected to each other by at least one wire. In addition, these oralternative configurations may be manufactured using a thin film ofmetal deposited on a liquid crystal polymer substrate. The electricallyconductive surface 88 measures at least one mm of length along the axisof the target nerve N and at least one mm of width along thecircumference of the target nerve N. In one representative embodiment,the strips 88 each measure about 10 mm×2 mm×0.0254 mm in length, width,and thickness, respectively. The geometry allows the molded elastomericbody 90 to securely hold the strips without migration, with the surfaces88 exposed for contact with the nerve. In the illustrated embodiment,the electrically conductive surfaces 88 are carried in an exposed arraycircumferentially against and along the axis of the target nerve N. Thisgeometry is well suited for applying neuromodulation stimulation, aswell as nerve conduction blocks, and has application for use in otherindications as well. Other geometries and configurations can, of course,be used for other indications.

a. Implanting the Nerve Cuff

Due to its mechanical and physical properties, the molded cuff electrode16′ shown in FIG. 29 is, in use, well suited for placement about aperipheral nerve to deliver a neuromodulation stimulation. This isbecause the electrode 16′ (i) reliably establishes and maintainscircumferential contact about substantially the entire nerve periphery,(ii) exhibits a predictable and repeatable diameter vs. pressure curve,(iii) is adaptive to post-operative swelling, and (iv) resists theeffects of translational and rotational forces to stay in placepost-operatively.

i. Implant Applicator Tool

As shown in FIGS. 37 to 39, the implantation of the electrode 16′ can befacilitated by use of an applicator tool 44. While tools of variousconfigurations can be used, the applicator tool 114 shown in FIGS. 37 to39 includes an applicator body 116 with a handle 118. As FIG. 37 shows,the applicator body 116 comprises an open ended, inverted trough forfitment over a portion of a target nerve N. As will be described later,the curvilinear form of the body 116 accommodates mounting of theelectrode 16′ in an uncoiled condition.

The applicator tool 114 also includes a slider 120 carried on the body116. The slider 120 moves along the axis of the body 116 between aforward position (FIG. 39) and an aft position (FIG. 38). Ascissors-type linkage 122 is coupled to the handle 118 so an operatorcan easily affect movement of the slider 120 fore and aft. Opening thelinkage 122 moves the slider 120 aft (see FIG. 38); closing the linkage122 moves the slider forward (see FIG. 39).

The inverted trough shape of the applicator body 116 is sized andconfigured so that, when the slider 120 is in is aft position, theelectrode 16′ can be uncoiled and mounted on the body 116 forward of theslider 120, as FIG. 38 shows. This is desirably accomplished immediatelybefore placing the applicator tool 114 in the targeted position on thetarget nerve N, which is shown in FIG. 38.

Closing the linkage 122 (as FIG. 39 shows), moves the slider 120forward. The slider pushes against the electrode 16′ and ultimatelyejects the electrode 16′ from the applicator body 116 onto the targetnerve N (as FIG. 39 shows). Free of the trough-shaped applicator body116, the elastic memory of the molded electrode 16′ causes it to coilabout the target nerve N, as FIGS. 33 and 34 show. The applicator tool114 can now be removed from the target nerve N, leaving the electrode16′ implanted about it.

The applicator tool 114 can be formed of a metal or plastic material.Desirably, the tool 114 is molded from snap together medical gradeplastic parts (e.g., polystyrene), and is supplied as part of a sterilekit with the electrode 16′ as a single-use device.

The applicator tool 114 makes possible a straightforward and reliableplacement of the electrode 16′ into humans and animals, e.g.,installation in vivo desirably is accomplished in one minute or less.

III. Implant Tools

The implant system 10 shown in FIG. 6 makes desirable a system ofphysician surgical tools (shown in FIG. 40) to facilitate implantationof the implant system 10 in the intended way, desirably on an outpatientbasis.

The surgical tool system 150 shown in FIG. 40 includes a needle 152 (ortrocar) and a companion introducer sleeve 154. The sleeve 154 iselectrically insulated or insulated except at its tip. The needle 152 isalso electrically insulated, except at its tip. The tool system 150 alsoincludes a tunneling tool 156.

The tool system 150 also includes an external pulse generator 158, whichoperates to generate stimulation wave pulses of the same type as theimplanted pulse generator 18. The external pulse generator 158 includesa connector cable 160 to couple the pulse generator 158 to the needle152. A patch electrode 162 is also included, which is to be placed onthe skin of the individual and coupled to the external pulse generator158, to serve as a return path for the stimulation waveforms.

Using the surgical tool system 150, the implant system 10 can beimplanted in the manner shown in FIGS. 8A and 8B.

In the above description, the surgical tool system 150 is used toimplant the implant system 10 in a single surgical procedure.Alternatively, and desirably, a two-stage surgical procedure can beused.

The first stage comprises a screening phase that performs teststimulation using a temporary external pulse generator to evaluate if anindividual is a suitable candidate for extended placement of theimplantable pulse generator. The first stage can be conducted, e.g.,during a nominal two week period. If the patient is a suitablecandidate, the second stage can be scheduled, which is the implantationof the pulse generator 18 itself, as described below.

IV. Implantation Methodology

Representative surgical techniques will now be described to place thesystem 10 in a desired location. Additional representative surgicaltechniques can be used as described in co-pending U.S. patentapplication Ser. No. 11/149,654, filed 10 Jun. 2005 and entitled“Systems and Methods for Bilateral Stimulation of Left and RightBranches of the Dorsal Genital Nerves to Treat Dysfunctions Such asUrinary Incontinence,” which is incorporated herein by reference. Theelectrode 16 and lead 12 are placed at the targeted tissue site (e.g.,in adipose tissue at or near the pubic symphysis), and the IPG 18 isplaced remote from the targeted tissue site. It is this desiredplacement of the lead 12 and electrode 16 that makes possible thebilateral stimulation of both left and right branches of the dorsalgenital nerves with a single lead 12 to provide sexual restoration(e.g., erectile restoration).

Before implantation, it is recommended that an oral broad spectrumantibiotic is given and continued for five days. The lower abdomen fromthe pubic symphysis to umbilicus and from the anterior iliac spinesbilaterally are prepped with Betadine (or Hibiclens Solutions for casesof Betadine allergy).

As before generally described, implantation of the implant system 10shown in FIG. 6 can entail a single surgical procedure or optionally atwo-step surgical procedure.

A. Single Surgical Procedure

The site for the needle puncture 60 is located midline or near-midline,near the inferior border of the pubic symphysis aiming toward the baseof the penis (or clitoris in females). Local anesthesia (e.g., 1%Lidocaine (2-5 ccs) or equivalent) is injected prior to making theanticipated needle 152 puncture site.

Once local anesthesia is established, as shown in FIG. 41, the needle152 is placed tip-first into the sleeve 154 and the needle 152 andsleeve 154 are advanced percutaneously into the anesthetized site 60 toa depth necessary to reach the target site between the pubic symphysisand the base of the penis (into the pelvis 4-6 cm rostral to the crus atthe base of the penis in proximity to dorsal genital nerve). As FIG. 42shows, the needle 152 is coupled to the external pulse generator 158(via the cable 160), to apply stimulation waveforms through the needletip concurrent with positioning of the needle 152. A patch electrode 162placed on the skin of the individual is also coupled to the externalpulse generator 158 to serve as a return path for the stimulationwaveforms.

The physician monitors patient-reported sensation or visible movement ofrelated organs, such as the penis, scrotum, or anal sphincter, (orclitoris for women), in concert with applying stimulation waveformsthrough the needle tip, penetrating and withdrawing the needle 152 asnecessary in a minimally invasive way, until a subcutaneous locationwhere optimal intended stimulation results are realized (e.g., bilateralstimulation of both left and right branches of the genital nerves).

When the desired response is achieved, the needle 152 is removed leavingthe sleeve 154 in place. The lead 12 is then inserted into the sleeve154. The lead 12 is fed into the sleeve 154 using a guidewire 155 downthe center of the lead 12 (see FIG. 43). A visual marking on the outsideof the lead 12 confirms it is fully inserted into the sleeve 154. Theguidewire is then withdrawn from the lead 12. Test stimulation isdelivered via the lead 12 to confirm proper location. The sleeve 154 isthen removed, leaving the lead 12 anchored in place. Confirmatorystimulation can again be applied to the lead 12.

Next, a subcutaneous pocket P is made and sized to accept theimplantable pulse generator 18. The pocket P is formed remote from theelectrode 16. The puncture site 60 where the lead 12 exits the skin isslightly enlarged with a scalpel. The tunneler 156 is then inserted intothe IPG site P and subcutaneously passed through tissue to the lead exitsite 60. The lead 12 is inserted into the tunneler 156 and the lead 12is passed under the skin to the IPG site P, where its connector is matedto the IPG connector. The IPG 18 and the attached lead 12 are theninserted into the subcutaneous pocket P (see FIG. 44) and the incisionsat both the pocket P and the lead site 60 are then sutured closed.

B. Two Stage Surgical Procedure

As before described, the first stage installs the electrode 16 and lead12 in the manner described above, and connects the lead 12 to atemporary external pulse generator 158. If the use of the external pulsegenerator 158 achieves the desired results after a predefined testperiod (e.g., two weeks), a pulse generator 18 is implanted in thesecond stage in the manner described above.

When the procedure is completed, the stimulus parameters for therapy canbe programmed into the IPG 18 by the clinician using the clinicianprogrammer 36. As previously described, the clinician programmer 36 maybe a Palm-based device that uses wireless communication to program thepatient's stimulus parameters up to two meters away from the IPG 18 (seeFIG. 12). Stimulus parameters (amplitude, pulse duration, frequency,duty cycle, etc.) are programmed to elicit the erection and becomfortable to the patient. The patient may turn the IPG 18 On or Offusing the patient controller, as previously described.

The various tools and devices as just described can be consolidated foruse in a functional kit or kits. The kits can take various forms. Asingle kit may include the necessary components for carrying out asingle stage implant procedure as previously described. Alternatively,more than one kit may be constructed for carrying out the two stageimplant procedure. Each kit also preferably includes directions forusing the contents of the kit to carry out a desired procedure. Theinstructions for use can also be available through an internet web page.

V. Representative Indications

Due to its technical features, the implant system 10 can be used toprovide beneficial results in diverse therapeutic and functionalrestorations indications.

For example, in the field of urology, possible indications for use ofthe implant system 10 include the treatment of (i) urinary and fecalincontinence; (ii) micturition/retention; (iii) pelvic floor muscleactivity; and/or (iv) pelvic pain; (v) defecation/constipation; and (vi)restoration of sexual function.

Restoration of sexual function pertains to both male and females. Malerestoration may include both erection and/or ejaculation actions, forexample. Female restoration may include both arousal (engorgement)and/or lubrication, for example.

The implant system 10 can be used for veterinary uses. The ability tocontrol/activate sexual actions such as erection and/or ejaculationactions may be used in animal reproduction technologies, such asartificial insemination. Artificial insemination is commonly used forselective reproduction of bovines, swine, dogs, and cats, asnon-limiting examples.

The implant system 10 can be used for deep brain stimulation in thetreatment of (i) Parkinson's disease; (ii) multiple sclerosis; (iii)essential tremor; (iv) depression; (v) eating disorders; (vi) epilepsy;and/or (vii) minimally conscious state.

The implant system 10 can be used for pain management by interferingwith or blocking pain signals from reaching the brain, in the treatmentof, e.g., (i) peripheral neuropathy; and/or (ii) cancer.

The implant system 10 can be used for vagal nerve stimulation forcontrol of epilepsy, depression, or other mood/psychiatric disorders.

The implant system 10 can be used for the treatment of obstructive sleepapnea.

The implant system 10 can be used for gastric stimulation to preventreflux or to reduce appetite or food consumption.

The implant system 10 can be used in functional restorations indicationssuch as the restoration of motor control, to restore (i) impaired gaitafter stroke or spinal cord injury (SCI); (ii) impaired hand and armfunction after stroke or SCI; (iii) respiratory disorders; (iv)swallowing disorders; (v) sleep apnea; and/or (vi) neurotherapeutics,allowing individuals with neurological deficits, such as strokesurvivors or those with multiple sclerosis, to recover functionally.

The foregoing is considered as illustrative only of the principles ofthe invention. Furthermore, since numerous modifications and changeswill readily occur to those skilled in the art, it is not desired tolimit the invention to the exact construction and operation shown anddescribed. While the preferred embodiment has been described, thedetails may be changed without departing from the invention, which isdefined by the claims.

Various features of the invention are set forth in the following claims.

1. A system for stimulating a left and/or right branch of the dorsalgenital nerves for the treatment of sexual dysfunction comprising astimulation electrode sized and configured to be implanted in a tissueregion at or near a pubic symphysis, an implantable pulse generator toconvey electrical stimulation waveforms to the stimulation electrode tostimulate the left branch and/or the right branch of the dorsal genitalnerves.
 2. A system according to claim 1 the stimulation electrodefurther comprising at least one elongated lead sized and configured tobe implanted in the tissue region, the lead including a cuff electrodefor placement on the left branch and/or the right branch of the dorsalgenital nerves, the cuff electrode comprising an elastic body having anelastic memory, at least one electrically conductive surface coupled toan inside surface of the elastic body, and the body and electricallyconductive surface assuming a coiled configuration in its natural shape,the coiled configuration allowing an intimate contact between theelectrically conductive surface on the inside surface of the elasticbody and the left branch or the right branch of the dorsal genitalnerves surrounded.
 3. A system according to claim 1 wherein thestimulation waveforms conveyed to the stimulation electrode affectafferent stimulation of the left and/or right branches of the dorsalgenital nerves, the afferent stimulation activating spinal circuitrythat coordinates efferent activity in the cavernous nerve and efferentactivity in the pudendal nerve, producing a sexual function.
 4. A systemaccording to claim 1 wherein the electrical stimulation waveformincludes at least a variable frequency component and/or a variable dutycycle component and/or a variable amplitude component and/or a variablepause component to ward off habituation.
 5. A system according to claim1 wherein the electrical stimulation waveform includes a variablefrequency in the range of about one Hz to about fifteen Hz, and avariable amplitude in the range of about 100 microamps to about 20milliamps, and a variable duty cycle in the range of about zero secondsto about ten seconds, and a variable pause component in the range ofabout zero seconds to about ten seconds.
 6. A system according to claim1 wherein the stimulation electrode is sized and configured to beimplanted in adipose tissue.
 7. A system according to claim 6 thestimulation electrode further comprising an elongated lead sized andconfigured to be implanted within the adipose tissue region, the leadincluding at least two electrically conductive portions to applyelectrical stimulation to nerve tissue in the adipose tissue region, andat least two expandable anchoring structures deployable from the lead toengage adipose tissue and resist dislodgment and/or migration of the atleast two electrically conductive portions within the adipose tissueregion.
 8. A system according to claim 7, wherein the at least twoelectrically conductive portions can be configured to function as twoindividual stimulating electrodes in a monopolar configuration or as onestimulating electrode in a bipolar configuration.
 9. A system accordingto claim 7, wherein each expandable anchoring structure includes twocircumferentially radiating shovel-like blade shaped members spaced 180degrees apart.
 10. A system according to claim 1 wherein only onestimulation electrode is implanted.
 11. A system according to claim 10wherein the stimulation waveforms conveyed to the one stimulationelectrode affect bilateral stimulation of the left and right branches ofthe dorsal genital nerves.
 12. A system according to claim 10 whereinthe stimulation waveforms conveyed to the one stimulation electrodeaffect stimulation of at least one of the left and right branches of thedorsal genital nerves.
 13. A system according to claim 1 wherein atleast a first stimulation electrode and a second stimulation electrodeare implanted.
 14. A system according to claim 13 wherein thestimulation waveforms conveyed to the at least a first stimulationelectrode affect stimulation of the left and/or right branches of thedorsal genital nerves, and the stimulation waveforms conveyed to the atleast a second stimulation electrode affect stimulation of the leftand/or right branches of the dorsal genital nerves.
 15. A systemaccording to claim 13 wherein the second stimulation electrode is sizedand configured to be implanted in, on, or near the cavernous nerveand/or the pudendal nerve.
 16. A system according to claim 15 furtherincluding a third stimulation electrode, the second stimulationelectrode being sized and configured to be implanted in, on, or near thecavernous nerve and the third stimulation electrode being sized andconfigured to be implanted in, on, or near the pudendal nerve.
 17. Amethod for treating sexual dysfunction comprising implanting at leastone stimulation electrode in tissue at or near a pubic symphysis, andapplying stimulation waveforms to the at least one stimulation electrodeto achieve stimulation of left and/or right branches of the dorsalgenital nerves.
 18. A system according to claim 17 wherein thestimulation waveforms conveyed to the at least one stimulation electrodeaffect afferent stimulation of the left and/or right branches of thedorsal genital nerves, the afferent stimulation activating spinalcircuitry that coordinates efferent activity in the cavernous nerve andefferent activity in the pudendal nerve, producing a sexual function.19. A method according to claim 17 wherein the electrical stimulationwaveform includes at least a variable frequency component and/or avariable duty cycle component and/or a variable amplitude componentand/or a variable pause component to ward off habituation.
 20. A methodaccording to claim 17 wherein the electrical stimulation waveformincludes a variable frequency in the range of about one Hz to aboutfifteen Hz, and a variable amplitude in the range of about 100 microampsto about 20 milliamps, and a variable duty cycle in the range of aboutzero seconds to about ten seconds and a variable pause component in therange of about zero seconds to about ten seconds.
 21. A method accordingto claim 17 wherein the at least one stimulation electrode is sized andconfigured to be implanted in adipose tissue.
 22. A method according toclaim 17 wherein a single stimulation electrode is implanted.
 23. Amethod according to claim 22 wherein applying the stimulation waveformsachieves bilateral stimulation of the left and right branches of thegenital dorsal nerves.
 24. A method according to claim 17 wherein atleast a first stimulation electrode and a second stimulation electrodeare implanted.
 25. A method according to claim 24 wherein thestimulation waveforms conveyed to the at least a first stimulationelectrode affect stimulation of the left and/or right branches of thedorsal genital nerves, and the stimulation waveforms conveyed to the atleast a second stimulation electrode affect stimulation of the leftand/or right branches of the dorsal genital nerves.
 26. A method ofusing the system defined in claim 1.